Best seat height low max rails vs fixed brackets?
 

Will going with an atomic rex style fixed bracket provide better headroom clearance than lowmax rails? Also why are some of the bride seats also labeled lowmax? Is it because the seat itself has better headroom clearance? Or is it just because those will be the only ones that work with the lowmax rails? I dont mind a fixed seat because no one else will be driving my car but ME!

Fixed side mounts will be the lowest you can get.

Will going with an atomic rex style fixed bracket provide better headroom clearance than lowmax rails?

I have Bride Vios III Japan on Lowmax rails. There is almost enough room for me to slip my hand under the seat. My FD does have that really base looking thin carpet, probably seat touches the luxury carpet.
I don't think I could put the seat lower as the bottom corners would hit the rails.

So, a fixed bracket should be able to get the seat another 1/2" down or more if you stripped/cut out the carpet.

Also why are some of the bride seats also labeled lowmax? Is it because the seat itself has better headroom clearance? Or is it just because those will be the only ones that work with the lowmax rails?

The Bride Lowmax system has several criteria.
Lowmax rails fit specified Lowmax seats to vehicles noted in charts with no modifications necessary.
Enables a low seating position.
Seat is perfectly centered to steering wheel.

I dont mind a fixed seat because no one else will be driving my car but ME!

If you don't have to sit with the seat all the way back the sliding rail can be nice to ease in/out of your harnesses, other than that the fixed mount will be lighter and safer (if they are steel and FIA, I wouldn't use Aluminum mounts).

I have the harnesses with the nice quick tensioners/release so I don't use this trick in my FD, but when I race my buddies Civic with clunky harness hardware I slide his seat back to untangle and forward to cinch up.

Would you do a 3 hour drive in those viosIII's? How comfortable are they? Looks like the shoulders would touch the door panel on an FD is yours in an fd? Clearance comments?

wthx100 Would you do a 3 hour drive in those viosIII's?

Yes, I have done several road trips including 7hr trip to Portland and 7hrs back and a regular 3 1/2hr trip to Medford to race.

I was worried before the Portland trip because in standard car seats I squirm around/adjust my position every once in a while to remain comfortable and in the Bride there is zero room for me to do that.

I didn't think about the seats again until I was prying myself out at the end of the trip (in Oregon they fill your gas tank as you sit there hoping they don't break your plastic gas tank flap).

How comfortable are they?

If the race seat fits you well it is very supportive and comfortable and you just melt into it.

I can only imagine how uncomfortable it would be if it fit you poorly.

Looks like the shoulders would touch the door panel on an FD is yours in an fd? Clearance comments?

Yes, the Brides are in my FD.
I don't sit with the seat all the way back; if I do push the seats all the way back the seat's shoulder area does rub the door panel a bit, but the door closes as normal.

If you sit in the FD with the seats all the way back the Brides wont fit you unless you are proportioned like a stork (all legs).

I was checking out the seating position in order to bring the weight back in the car with racing class allowed pedal/steering wheel extensions.