I am aware of SMR's draw backs they were horrid 10 years ago but they have got better so this doesnt bother me as i am technically archiving stuff also since there will quite a few drives and there all 2tb rebuilding the pool shouldn't actually take that long.
Some of us have delt with SMR drives and have actual freenas experience using them. just because you have "quite a few drives" wont make the rebuild faster. TBH slow rebuild with SMR is only 1/4 of the reason there considered a bad idea.
Freenas works great, but its important to make sure you dont do any of the "DO NOT DO's"
Members have pointed out alot of DONTS, but you seem to have a reason as to why you are going to do them anyway.