I know that others have replied but will chip in from my own experience.
I mainly use US psn and get my membership for ps plus on it too. Usually I buy codes online when there are sales.
Game wise I think sg region is most convenient because we can use local cc. On the US one you cannot do that, have to use prepaid cards unless you have a US cc. I sometimes get games from sg psn and also us psn.
Honestly doesn’t matter if you get physical. Just make sure you got that region acc if you want to buy. I think nowadays there’s a lot of region 2 games (Uk/eu), so for those the dlc will be only accessible via their psn region.
Also just take into account that if you get games digitally and want to play immediately at midnight on release; sg psn is the way to go. Us one will be next day 11 am - noon due to unlock time diff.