Muscles weight quite a bit, can't see how having muscles in the arms will benefit a table tennis player - just look at the top players, be it table tennis or normal tennis - they all have no muscles in the arms. Then looks at them from the waist down - different picture. Having muscles don't make you athletic, quite the opposite actually. When i got to the gym and do my arm sessions and then do a TT session in the evening i always feel quite stiff. Plyometrics is what's probably best imo.
You cant even play a sport without "having muscles in arms" btw.
And if top players dont look like a fitness models it doesnt mean that they dont train those "muscles in the arms", a lot of people, i would say most people that are casually going to the gym looks like regular people, but they lift weights for years. To look really muscular or jacked you should have genetics for that, or you even some one need to take a PEDs for that. And, as i already told, you dont need that bodybuilding style of training for tt.
Sprinters runners, rowers, swimmers, all are doing weight lifting for running/swimming/rowing faster - i dont see why it cant be beneficial for any sport including tt.
If you feel stiff after a strength training - go to a massage or some stretching, or swimming pool. You can get stiff by just playing a lot of table tennis, and when it happening - you most of the time is doing the same - massage, stretching, etc.