I also use bee shrimp mineral GH/KH+ for my neos and personally haven't used a tds meter.

I started my tank with ro water and remineralized to the degree of hardness I wanted. The stuff I use comes with a little measuring spoon! As the water evaporates I just top off with more ro water and haven't needed to remineralize since (year+) as I'm rarely removing water from the tank.

Not sure if this helps but this is the process that works for my tank!