Red Sea blue bucket, mixes to the alk I keep my tank at. Before I switched to Red Sea a few years ago I was using Aquaforest. Only switched because Aquaforest was out of stock everywhere for a while and eventually couldn’t wait for it to be back in stock. Saw no major difference so just stuck with Red Sea since it always seems to be available.
Even using Fritz RPM blue box for the past month just like everyone else it mixes where I want to be and the LFS carries it so I don’t have to order online. They also carry aquaforest but opted for the fritz. Time will tell as other have had issues with SPS with fritz.
Honestly I rarely check parameters after mixing it. I only change 2 gallons a day in my 125g so any inconsistencies wouldn't make much of a difference in the tank.
The few times I've checked it the cal/alk match up to the chart that I often see referenced on this forum (I don't know the origin of the chart).