The metal lined holes might be connected to ground so shouldn't be anything to worry about.

As far as fasteners you could always use bolts and plastic / nylon nuts. Be very careful on tightness or you will warp the board and most likely break solder connections. Nylon bolts also exist.

I've also used zip ties. Stick zip tie from top to back of board and use the head of a second zip tie as the holder / tightener. Works best if you have matching springs to dictate the tension.

gf3 wont need much pressure so not an issue, but for more modern stuff you want back plate preventing pcb from warping and ripping bga joints under the chip.
as for holes its always better to be prepared than surprised https://www.youtube.com/watch?v=fjUscSRLwks my hack is to buy screws one size smaller than holes and sleeve heat shrink tube. I also used angle grinder and some random piece of metal to make my own backplate for Xeon cpu 😀