I know I don't have an amazing GPU, but I'm able to run CS2 at medium graphics with ~90 FPS average, similar with most other games. However, running s&box at 1080p on the minimum graphics, I get 20 FPS. Has anyone else experienced this low of performance? If so, are there any plans on lower graphics options or just more optimization updates?

If I change my display settings in s&box to be Exclusive Fullscreen at 1280x720, I still only get 50 FPS at minimum graphics.

For reference:

CPU - AMD Ryzen 5 3600 6-Core
GPU - AMD Radeon RX 580 2048SP
RAM - 32 GB (DDR4)

pre scene mapping i would just say meh who cares just wait until s&box gets optimization , but now after recreating several maps in scene mesh, I heavily agree, I run an rtx 4060 with a *cough* *cough* i5 :c , and my hammer maps back then would run fine 100+ fps, I remade a few old source maps, and my performance has drastically gotten worse on them especially, layla, please triangulate my scene mesh or somethin, it's really bad 

also s&box is meant to run on anything in the past 10 years isn't it? why do we have more modern gpus and cpus not even hitting 140 fps on some games

4 or 8 gb of vram on your gpu?

There's an important point - s&box is both a platform and an engine, and it can be used to develop a wide variety of games, some of which can eat up all your FPS (4k textures, lots of highpoly models), while others will run on any specs. 

Sadly but, s&box still has a ton of optimization issues, and FP work on it. You can quickly skim through the last three devblogs and see that it's just not a quick job - https://sbox.game/news and imo, less than 6gb vram will be really bad for s&box anyway

I also recommend jumping straight into the game from the main menu as soon as possible. The main menu still has serious performance issues. If you want take the potato, but with the high fps, just press in F2:

r_shadows "0" 
r_postprocess "false" 
r_3d_skybox "0" 
r_enable_volume_fog "0" 
r_enable_cubemap_fog "0" 

I believe that performance in S&box is a serious problem. I'm from Brazil, and judging by your specs, I believe you are too. I have a Ryzen 5 4600g, RX 570 4GB, and 32GB of RAM. Running benchmarks, I noticed the following: performance in S&box is severely inferior to CS2 and even Half-Life: Alyx, on which the game is based. The main problem seems to be video memory consumption. Here in South America, most people have more limited computer configurations, especially GPUs, due to high US tariffs. The game seems to utilize the CPU very well; my Ryzen 5 seems more than sufficient. RAM consumption seems relatively low; 16GB seems sufficient in most cases. The real problem is the GPU; GPU usage is very high, even in simple games like Sausage Survivors 2, which ran with the best performance of all games,  it seems to scale memory very bad for 4 GB of video memory, in the sandbox mode, it allocates more than that to about 6-7 GB and starts using the PC's RAM, causing performance to plummet. If any developers are reading this, I think this is extremely important, since GMod itself is very popular in South America and Eastern Europe. 

I love this game but the fps can drop from around 170 to 80 when shooting from the magic mp5 gun that spits out bullet hell tho. I have rx 9060 xt and r5 3600

Sorry for not following up on this, I haven't been focusing on s&box and forgot to check back here.

In response to Skipin: 8.0gb Dedicated, 16.0gb Shared.
In response to Titanovsky: Unfortunately, since the open-test is now closed, I can't try this out, but I'm sure it would've probably helped, so thank you :)
In response to Lord Rivers: I'm not from Brazil, but the U.S.A. I just don't have the money to buy the high-end RTX cards unfortunately. I hope the s&box devs push some GPU optimizations by the release date. It's obviously not a low-end game, but I don't think it should run as poorly as it does.
In response to chill unc: My FPS drops aren't as noticeable, since it'd go from ~40 to ~20, but wow, shooting a weapon should not cause a 90+FPS drop.