I've used various things. First, I prefer the button it came with. However I had some tops NOT come with strings, or some without buttons(and crappy strings).
I have a small supply of I think they are 1" wood beads with small holes I bought a while ago for a different project. I only needed 1 for the project, leaving me the rest for "whatever", or around 20 or more. With the 2 "Daiso Japan" tops, I ended up with crappy strings and no buttons. I ended up going to Michael's and getting the 1.5" wood discs and drilling holes into a small quantity. so I would have extra.
I also thing I have a few Duncan buttons. Some of my Strummol8's use what are basically poker chips(real deal, not the generic varierty). One of my Chico tops uses a real poker chip from a local game casino, while the other uses a wood disc.
For me, I don't have issue with the weight of any buttons. If it does the job, I'm good. Maybe when I get better it will make a difference.