Having trouble with information not matching between Datasheets, lookup sites, and the manufacturers website to make a purchase.

Trying to max out a pc I inherited to give to another family member but having problems trying to confirm what memory I should purchase and trying to work my way through it but just need some clarifications or maybe I'm missing something. (trying to make this purchase and "finish" this pc to it's max capabilities before prices start to spike)

The pc in question is the HP 280 G3 Microtower. Originally I got the tag FX-ISL-4 off of the MoBo but couldn't find specs so with CPU-X it pulled up a HP 8350 (1) MoBo that I could get specs from (am I missing the 8350 on the board or is cpu-x style programs the only way to get the info?). H110 intel chipset LPC/eSPI controller.

Has an Intel Core i3-7100 (2) with integrated Intel Mesa HD Graphics 630.

Currently it's running 2 - 4GB ddr4-2400Mhz. This all started with trying to figure out the right CAS latency to get as a site listed different ones and I wanted to make sure the more-expensive/low-latency one would even be worth it or would be reduced and ineffective to get the better one. All of the sites also suggest a 32GB kit with 2 - 16GB ddr4-2400/2666/3200 (newegg,kingston,crucial) with the CAS Latency all over the place (I know it's a formula, gonna have to go back and refresh my mind on that I think).

When I ran into the Mobo datasheet (1) it states "Supports up to PC4-21300 (DDR4 2666), Supports 4 GB and 8 GB DDR4 UDIMMs" (making only 16gb total possible). The cpu (2) says ddr4 with "Rated Speed: 2400 MT/s" making all of the other ram recommendations overpowered.

I know from a previous Mac Book pro upgrade the manufacturer specified only 8gb but you could actually install 16gb with updates and changes. I can't find any documentation or articles but the memory sites are very adamant I can install 32GB worth on the HP and I'm very tempted to pull the trigger on that with the lowest CL I can find.

Any suggestions or steps I'm doing wrong? Really want to be confident with identifying my parts, understanding the specs and interactions, and being able to be confident that the parts are compatible. I have a bunch of others I've been staring at to work on similarly but I always hesitate, helps when it's not going to be your computer to actually do the thing.