I'm guessing from your location that you are likely to be fishing for grayling in upland rivers which are likely to be fast and shallow. That's similar fishing to my own and I gave up on piddly little stick floats years ago. They have their place, but it's not on fast shallow water for grayling. For many years, fairly standard Avon floats were my go to choice. However, I went to the Dave Harrell Avons. A couple of years back, I progressed to Bolo floats. Not really what they are intended for, but they work just fine.
Ultimately, my advice would revolve around a couple of points. Don't be scared to use fairly big floats. I tend to go for 3,4, or 5g. Despite the gut feeling that they'll be insensitive, I've had no problem seeing bites from minnows and tiny dace, even at fairly extreme ranges. Don't be scared to shot these big floats with bulk shot, or even olivettes, well down towards the hook. Whilst grayling in fast shallow water will come up in the water if you overfeed, they are basically bottom feeders. The need for fancy shotting patterns is usually minimal.