Slowing Down Render For Better Quality?

Is there any way I can tell Da Vinci Resolve to "take its time" rendering my project, e.g., perhaps changing the "Quality" setting from "Automatic:Best" to the "Restrict" option? I've noticed that some of my renders have artifacts and issues, particularly on segments that are imported MP4s or have some type of color grading applied to them. Changing the format to "Quicktime" (instead of MP4) seemed to improve the rendered video, but there are a few issues remaining. Is there any other way I can tweak the render settings to decrease the chances of errors/artifacts in the render?

My other settings, for the record, are as follows:

H.264
1920 x 1080/ 30 fps
Quality: Automatic: Best
Key Frames: Automatic
Frame reordering (checked by default)
Data Levels: Auto
Use render cached images (otherwise Resolve crashes on certain Fusion comps while rendering)
Bypass re-encode when possible (checked by default)
AAC audio

The "disable edit and input sizing", "force sizing to highest quality", and "force debayer to highest quality" are all unchecked (as by default).

Thank you for any suggestions. This is all still in Resolve 16, btw.

So, I found the option where the render speed can be reduced, but a prevailing sentiment seems to be that lowering render speed won't actually affect the quality of the render. Rather, it'll just...slow it down.

So the other options people have suggested for "artifacts" in render are:

1) Checking off the "frame reordering" box in the render settings on the Delivery page;
2) Encoding in a different codec than H.264 (e.g., MPEG).

My question is this: if I encode in MPEG (e.g., Quicktime format with MPEG4 video Codec), is uploading such an encoding directly to YouTube a good idea? Google says they support MPEG4 as a file format, but I keep seeing posts on here about converting back to H.264 (which, I presume, would be done through Handbrake?). If using the MPEG4 codec is perfectly fine for YouTube, is there any point in converting back to H.264 afterward?

Thanks for any suggestions!

Reducing the render speed does not affect quality. It does give lesser systems more time to do their processing.
Quicktime and MP4 are container formats. Both can contain a range of codecs including h264. YouTube is quite happy with a variety of codecs. You can upload Pro Res, DNxHD, Cineform, etc. File sizes are much bigger and upload times are much longer of course. YouTube re-encodes everything you upload, so you need to upload the highest quality you can in the first place.
The footage I edit is h264 in an MP4 container and is 1080 50fps 35Mbps. To counteract the artifacts in YT I upscale to UHD and use the "Best" setting.
These are the supported formats you can upload to YT.

Thank you for that summary, Charles Bennett! I previously tried upscaling to UHD, but there were still a few artifacts appearing here and there, especially where sharp and quick contrast changes occurred. Do you think experimenting with, e.g., UHD in a MPEG4 codec (or in H.264 with frame reordering turned off) would be worthwhile?

I had an issue recently with a complicated 4k render. I kept getting weird artifacts and green flashes, even when rendering to Dnxhr at 50% speed.
What finally saved me after a day of frustration was going to the complicated parts (h.265 footage with a lot of layering and compositing, speed ramps, noise reduction, etc.) and doing a render-in-place for the footage. Just switch the default settings to a higher quality render at the resolution you need (I used dnxhr SQ or HQ at full res) and choose the option to include effects.
The final result was a much faster render with no artifacts.

Definitely something funky going on under the hood I think that needs to be addressed. It should be noted I'm not exactly on a crappy machine... 14 core i9, 96 GB ram, and a GTX 1080Ti.

Haha, not exactly crappy at all (96 GB ram!). I did a test on one of the portions exhibiting artifacts by rendering it with "frame reordering" turned off (MP4, 1920 x 1080). No artifacts. I'm guessing that rendering it in the MPEG4 codec will also produce no artifacts, since the "frame reordering" option doesn't even appear for MPEG4.

So at this point, I think I'll render it at MP4, UHD (higher resolution seems to lessen chance for artifacts when uploading to YouTube, as Charles Bennett suggested), with frame reordering turned off. Hopefully that eliminates all artifacts.

I'm still on Resolve 16, by the way, so I don't think I have access to H.265 or Render in Place options, but I'll keep those in mind for 17!