One thing to consider is how close your hotel is to the railway station in the place where you are based. Luzern can work for that as there are hotels very close to the railway station but you have fewer options in some other places (eg. Bern).

Although Switzerland is not a large country, it can take time to get from A to B because there are mountains "in the way". For that reason, I'd think about whether there are specific sights you want to see. For example, while Luzern works well for Pilatus, Titlis and the Lauterburnnen area (and that might be more than sufficient for five days) it's far less convenient for Zermatt and the Matterhorn.

I always use the swiss travel pass in Switzerland (https://www.sbb.ch/en/tickets-offers...avel-pass.html). You can buy one at the railway stations at GVA or ZRH. There's great convenience in simply being able to get on any train, bus or ferry without buying a separate ticket each time. Also, if the weather is poor and you want to spend the day looking round a larger city, it's free to get to that larger city if you have the swiss travel pass. Unfortunately, there isn't a five day pass, you have to choose four or six days but the four day flex pass at least lets you choose which four days in the trip are covered by the travel pass. I always buy the 2nd class swiss travel pass. That is partly because in my (I think) seven purchases of one, I've yet to find myself on a Swiss train with every seat in 2nd class occupied. It's also because the rack railways, funiculars, cable cars etc. for which you get the 50% discount don't have 1st class so that benefit of the swiss travel pass is identical whether you have a 1st class or 2nd class one.