Technically, most motherboards can handle mixed memory ok. But, if you run different speeds and latencies of memory, it will all run at the speed of the slowest module.
Most games are fine with 16gb of ram, though some can use more if you download a ton of assets and/or mods such as cities skylines.
Music production usually does OK with 16gb of ram too. The only case with music production is if you have tons of samples/libraries in which case you may benefit from 32gb of ram.
Unless your use case has you needing 32gb of RAM, its likely a waste of money to buy the extra RAM unless you are just lazy and like to leave all your music production software up and running in the background when you have 500 tabs open in 3 different browsers and decide to play a memory heavy game at the same time... but even then, the computer will just swap the stuff in the background and still run everything generally ok, especially with a semi-decent M.2 SSD.
If you insist on getting more ram, it might be worth keeping the 16gb for now, and, if in 1-2 years you need the ram, you can always buy the ram in the future. (And hopefully, it will be cheaper too since RAM is expensive currently due to all the price fixing in the market)