Maximum number of connected sensors?

Yes. At least with ANT. As well as a Tempe. I seem to recall the max is something like 8 ANT sensors. BT it's lower but I don't recall how many.

I regularly connect both ant+ footpod and ant+ hrm at the same time, also at the gym I use Bluetooth HRM and ant+ footpod.

When cycling, I use an HRM strap, speed sensor and power meter (all ANT+), as well as a BT connection to my phone.