I did all 3 on my first trip by myself in 1997 and also 3 with 2 friends in 2000. The Lonely Planet guide had a good section with lots of info on the temples, and there were always these kids that spoke amazingly good English that'd approach you and want to be your guide at that particular temple. In 1997 I stayed at a $4/night guesthouse with a fan and mosquito net and mandi-type toilet, and the $6/day moto driver didn't double as a guide (he just set up a hammock as I walked around, reading the part in the Lonely Planet. I had a few of the places to myself. By 2000 there were a lot more hotel choices already and the friends insisted on hiring a car driver, which made sense anyway with 3 people. It was also possible by then to get to Banteay Srei without an armed guard (which was still needed in 1997 and I didn't go for)

Sections like the Roulous group tend to separate the curious from the templed-out.

Phanom Rung and Phi Mai are well worth it, and I've just missed a chance at Preah Vihear on 2 occasions now (it was near Pol Pot's last stand). The Thai sites are in Isaan, which I've always found pleasant to visit (and cheap) but doesn't have many blockbuster attractions.

Also got to Luang Prabang circa 1998 and 2002 and I'm sure it's more built up now but probably still with a lot of charm. It used to be that the daytrips could give you a lot of the hilltribe experience that the tours out of Chiang Mai had to go further and further to find because Thailand is a lot tamer than it was. Not sure if that part is still the same.

OP sounds like she's not interested in so many temples. That really is a lot.

One place in Cambodia I haven't managed to get to yet is Battambang. I don't know if anyone has thoughts on that area.

I've done quite a bit of the rest of the country though. The eastern half is a lot less visited by tourists. My most recent trip was to that side of the country from PNH. It ended up being long drives but there's some really beautiful scenery.

Likewise Laos has beautiful natural scenery. It doesn't get a lot of tourists. I did the 2 night Mekong cruise on the Vat Phou a few years ago. It goes more or less from the Cambodia border to Pakse (although stretches at the beginning and the end are on long boats instead of the bigger boat due to river conditions. It was an interesting trip though and the sunrises and sunsets were really spectacular. Once we got back to Pakse I spent a couple of days touring the Bolaven Plateau. Great waterfalls. Coffee plantations.

But 11 days is not a huge amount of time. So I guess Luang Prabang makes some sense (although I know there are some strong differences of opinion). There are flights between Siem Reap and Luang Prabang (not always non-stop though) so getting between them is fairly easy. LP is pretty quiet though. Other than some day trips up the river, Kuang Si waterfall, and the various Buddhist temples around town how much time you spend there is up to you and your need to have something to do.

Certainly there are options. The trip report linked below has lots of pictures

Lol, it's been a while since you needed caution at Banteay Srei. Now it's just a matter of avoiding the crowds, not Khmer bandits. Road is good, too.
I get a guide/driver each trip and have for years (same guy). They know the back ways to avoid the crowds at places like Ta Phrom.

Roluos is pretty good, not particularly distinct, but a lot of temples in a relatively small area. Now there's an air con Makro warehouse store on the way. :rolleyes:
Instead, if you're ok with hiking uphill on a dirt path, I'd do Kbal Spean combined with Banteay Srei. Carvings in the river bed are unique, in my experience.

Preah Vihear is only approachable from the Cambodian side now for access to the main features. Unmissable, if you're in the area. Like Wat Phu and Phnom Rung, it's axial, not rectangular, and beautifully positioned on the cliff top overlooking the Cambodian plain. Highly recommended.
Day trip (long) possible from Siem Reap, though there's ok lodging not that far. Some lesser bas relief and small stupas only on the Thai side, easy day trip from Kantaralak.

Luang Prabang isn't particularly built up in the old quarter, though there are resorts springing up outside that more or less protected area. Still a good place to hang out. Phusi Hill is ok in the early morning, but avoid at sunset. Kuangxi Falls is a zoo.

Travelfish has a lot on Battambang and Bolaven plateau, including the waterfalls.
(I reference them a lot because they're high quality and generally a replacement for the Lonely Planet guides we all used in the 1990s, but don't have a financial interest.)

Just came back from Cambodia. No need to avoid Pub Street.

I did 3 days of temples. Was way too much.

It's a pretty small town with a couple of things for tourists. The bamboo railway is gone and has been replaced with something that's not at all like the old one. There's a couple of neat temples and the bat cave is nearby to them. Let me know if you have any other more specific questions.

Have you actually tried google 'cambodia visa online' and spend five minutes to go thru first page of results?
The very first result is the official online visa application site - fill your details, upload photo, pay $35, get confirmation email, print it, present at the border...

I don't know where you are, but for me it is true. First two results are official government website results.

LMGTFY

You can get the eVisa for $36 online, paid by credit card, or pay $30 at the airport with an unpredictable, but possibly long queue for visa on arrival. Official eVisa site.

Get the eVisa. It avoids the queue and also the dumb full page visa sticker since the eVisa is a print-yourself that you staple into your passport and toss after you leave Cambodia.

Depends how you feel about temples :) 3 days was too much for me but I can understand why some people would spend that much time doing it.

So 8 days on the ground? I'd skip Battambang and Koh Rong Samloen/Sihanoukville. Sihanoukville is a toilet and travel to/from in your time constraints doesn't make sense. Luang Prabang also not really possible. I'm basing this on recent, last month experience, and maybe 20 visits.

22 Nov: arrive PP (from where? Jet lag recovery? Grab (Uber like) to town); eVisa
23, 24: PP (Penh House hotel on Street 240, book using Agoda; Grab to get around)
25: travel to Siem Reap, take Giant Ibis bus (6 hours end to end); stay at Angkor Village, Wat Bo road
26 27 28 29: SR, 3 day temple ticket + Angkor Museum. Get a guide/driver in advance. 3-day pass is valid for 10 days from the issue date
30: travel to PP. Giant Ibis bus
Before flying from PP to/from SR, work out the time. I think I may in the minority recommending the bus, but I also may be one of the few here that's done both and recently.
1 Dec: leave (allow 1 hour to get to the airport, use Grab)
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Rich