With raid 10 - i would not risk it . With RAID6 ( obviously not on BTRFS) it is fair game if you have solid return policy for drives which are DOA. Go for SAS drives, they are cheaper (but generally hotter and nosier). And look for old-new-stock on specialized sites, no one in enterprise needs say 8tb drives, so they selling them cheap at times.
Get drive, connect , run long smart self-test ( for 18tb it is probably take a day). If it passed you are reasonably sure that it will not die soon. And keep running these test regularly, as soon as they start failing, replace.
A4-6210 with build in GPU has TDP of 15W. There is no point to optimize anything it is seeping power already. may be try to use tlp to limit max charge level of the battery ( i’m not sure is you laptop is supported). You can play with governors too, but I personaly will not bother. You obviously need multiuser.target but not GUI.