I am looking to fly a rtw trip with oneworld this summer and i had a couple of questions since i dont know mych about oneworld since i usually fly skyteam.
First of all this will be my route:
ARN-LHR-HKG-BKK-HKG-SFO-MIA-CCS-JFK-LHR-ARN in F and some parts in C.

I was wondering for the first leg i could also take the direct LHR-BKK with either BA or QF but think service on CX is much better then the other 2.
Also is it worth flying C class on MIA-CCS-JFK on AA since otherwise i just buy a economy class ticket for those legs saving me one continent.
What is the best program to credit the miles to since i wouldnt be flying oneworld much i am not looking for status or something just to maximize my miles for a reward ticket, i was thinking AY since they give you 3 times the miles for first class travel but i am not sure about their redemption policies.
Thank you very much in advance!

Wow, lot's of questions. So where to start? The routing. Your itinerary is fine and valid. However, it is not optimized in any way. Which means it doesn't make use of the possibilities a AONEx offers. It all depends on how much time you have available.

If you want to optimize, add some segments in North America and maybe a long flight to the middle east in Europe. You can get a nice flight on BA F to DOH, MCT etc. for free.

Weather it is worth adding a continent for a flight to CCS is up to you. The business class is nothing to write home about but still nicer than economy of course.

In terms of redemption value, most people here prefer AA because of the low taxes and you only need very few miles for awards. You will even be able to get status with them via the Platinum Challenge if you have enough segments on AA. Be aware that AAdvantage doesn't earn miles etc. on US TATL segments so you need to go to LHR with AA not BA if you credit to AA.

Your itinerary would be okay with one caveat - you'd have to connect at JFK and not stop over there, hence ARN-LHR-HKG-BKK-HKG-SFO-MIA-CCS-xJFK-LHR-ARN.

One alternative you might look at would be using the North America flight allotment (6 segments) to get you as close as possible to CCS without leaving "North America" and then fly on a separate ticket from there, e.g. ...SFO-MIA-SJU-CCS-SJU-JFK... so as to save the ~US$1000 for the 4th continent.

Many people these days are thinking that service on QF is becoming the equal of CX on premium longhauls, but it's a personal thing.

As for miles earning and redemption, you need to look carefully at your flying patterns and at the individual FF plans' "earn/burn" ratios. A business or first class RTW can provide a rich harvest in miles and/or status, but the miles/status will only help you if it supports your own travel and flying plans and preferences.

Welcome to this long standing debate. I have also tried LHR-BKK in F a number of ways, -- BA to CX through HKG, CX through HKG, and QF direct. I find the QF seats not particularly conducive to sleeping, and far too many seats in the 744 F cabin. Also, there's absolutely no privacy in the F seats (note, not suites) on QF. Not even some type of enclosure as on BA, let alone a legitimate suite. That said, the service is warm and friendly, and the food is great.

BA has the standard BA 744 F seats, service and food. Service a bit formal, but otherwise a good and consistent product, both hard and soft. The seats do afford some measure of privacy, and the fact that they're angled out (window seats, that is) enhances that. And, despite the numerous posts on EF from others, I have never had a bad service experience in BA long haul F.

The new CX suites are unbeatable, IMO. Extremely comfortable, and well suited to a good night's sleep. I have always found the CX service perfect, but I am aware that some find it a bit on the subservient side. My CX FAs have all been appropriately solicitous, accommodating and, yes, friendly. If you like Asian food, then this is the hands down choice for you.

So for me, this route will continue to be LHR-HKG-BKK on CX, but try them all and see which you like best.

Enjoy !!!