@eelz I’m not sure what you mean by control board for the ESCs. The power to the ESCs comes straight from the F550 (which is a power distribution board as well as a frame). The control (data) lines from the ESCs plug straight into the pixhawk. So you don’t need anything more than the ARF kit you’ve got.
The telemetry is useful as it gives you realtime data and control on your laptop/tablet. It is possible to control it solely from this, but very very very much not recommended, particularly if this is your first UAV. In fact I would go as far as to say it would be dangerous, irresponsible and almost without doubt you will lose the entire setup without an actual TX/RX setup - it will fly off and you won’t be able to control it in time with just a telemetry link. Get yourself a Taranis kit or something similar, that has the tx and the rx unit combined. They’re relatively cheap and easy to setup. Once you start flying you’ll understand why it’s absolutely necessary 