CSGO vs CS2 using SQM

[Hudra]

Please have a look at this Topic:

Why you need at least 3Mbps upload to get good game performance with ~1500byte packets: Doing the math

There are many people who try hard to game on slow asymmetric lines such as DSL with 768kbps upload. Because cake and SQM do such a good job, they often think they can just tune it right and they'll get good game performance, but they find that no matter how much they tune things, it just never works well when someone else on the network is doing something. So I posted a blog post that does the math and summarizes why even though games only use a few hundred kilobits per second themselves, you …

I don’t have any experience with CS2 but after a quick search I found this video about the the subtick system you mentioned. What I can see is that the packet size drastically increased with CS2’s Sub-tick servers + it seems like there are now 2 packets sent per tick (or could be fragmentation):

So it looks like the game uses way more bandwidth now and with your limited upload bandwidth this could be the reason for your issues.