Ive been using IO salt since I started my tank with the ZeoVit products. I dont wotty too much about the Alk differences for water changes, but I will say that it is harder to manage 2 part dosing with IO, as the parameters seem to drift from batch to batch. I check my Alk everyday so I can keep an eye on trendings, but the size of your WC is going to have a bigger impact on the parameters than the parameters of the water you use to replace it - meaning that a 5 gallon WC with 10 dKH water on a 100 gallon tank with 8dKH wont have near the impact on parameters that a 30 gallon WC with the same saltwater mix.
I did recently purchase a small container of RedSea blue bucket salt and I found that Im not tweaking my 2 part dosing as much because the salt is relatively stable throughout the whole mix. I may move to it in the end, but IO does work with ZeoVit - you just have to know what the trade offs are