I will answer a little indirectly. With my 40 Watt CO2 laser - K40, which is realistically a 30-35Watt machine, I cut “normal” wood to approx. 6-8mm, MDF / HDF I have only had 3 and 4mm to work with and here there are no problems at all.
Acrylic I have, just to test it, cut 16mm, (I do not want to work with 16mm all day …) but 1-8mm goes well and in 6mm I have had a small production series with very fine results.
Plywood, - if I buy “laser plywood” then 6mm is no problem, if I buy 3mm plywood from my hardware store - I can be unlucky and use 2-3 rounds and the result will not be so nice. The quality or composition of standard birch plywood varies so much that it is often a lottery game how I can work with the material in a laser. But “standard” 3 and 4 mm can be used about 75% with good results the rest takes more time or can not be used at all.
I consider a useful result if I can cut a material without it getting too dark in the cut and with only one turn. In rare cases, I also accept 2 rounds if I do not have another choice. But I prefer to buy a good laser quality plywood, life is too short to get angry over poor results.
I use standard equipment, no fanci mirrors or lenses, air support and a CW500 cooling machine. The latter is a bit expensive but the small aquarium pump and a bucket of water which eventually becomes “alive” and has lots of oxygen in it, I do not like.
If you buy a 50 Watt machine, it is probably a real 40 Watt machine, you can start from my “data” and add a little more, then you are on the right side of what you can expect.
Maybe someone with a 50Watt CO2 laser can come up with more concrete data?
If you are seriously interested in a CO2 laser and might want to make some money with the machine I would recommend at least a 60Watt tube and as large a bed as possible.
I am about to buy myself an 80 Watt machine and am already looking forward just like a small child.
Hope I could help you a little
Good luck with your choice.