Being a Dell tech doesn’t mean they know what thy’re talking about unfortunately. There has been a lot of controversy surrounding the Dell 32" inch monitor, because it is “Freesync” compatible (not Nvidia Gsync Compatible) and most reviews on it have proven that Gsync does work even though it’s not certified Gsync. As long as the games you play keep an FPS between 48 - 165. The Dell tech probably knows this, but doesn’t realize that you’re going to play FS2020; which does not need Gsync to play and max FPS is 60.
Now, let’s say you play other games down the road besides FS2020. The monitor will absolutely play those games and is compatible. If you don’t turn on Gsync; they will play and run optimely without issues. Gsync is just a tech that matches FPS with the graphics card to the monitor refresh rate (so to speak). Not required to be turned on like I said.
It’s interesting that the Dell tech said that monitor is not compatible yet he doesn’t know that a 550w PSU is not recommended for a RTX 3070.
Nvidia recommends a 650w PSU for the RTX 3070; that’s with a Intel 10900k which you got an 3700X and will work, but if you ever were to upgrade the processor, you SHOULD go up with the PSU, but would already have it.
Bottom line; I could be the manager of the Dell techs. Use Dell to buy the system and for the Warranty. Listen to us for what you should buy. That’s my recommendation. 
Ultimately you bought a very good system; the Dell 32 will work and you will like it. If you are still searching for a monitor; buy the Dell 32 from Best Buy online. You can plug it in and use it and you will see that it works great and you will REALLY like it. If for any reason you don’t like it, Best Buy has a 14 day return policy even on opened items. No re-stocking fees; they just re-sell it as an open box item.