You definitely don’t need a QX7 to start off! The learning curve for OpenTX is steep, it’s hard to get set up if you have never done any plane stuff before, despite video tutorials etc. I started with a $50 transmitter with dual rates, expo and 6 channels. It took an evenings work to figure out and set up all my models. It took me 3 weeks to get my sons Jumper T12 on OpenTX working right.
As for the electronics, have you put the servos in? You need the elevator and aileron servos centred and installed in both those planes before you complete them.
Receivers- buy the Flysky package which comes with a receiver.
Motors- I use this motor
which is under $5 with a
20A esc in both my TT and SE5. It gives good performance in the TT on 2s and the SE5 on 3s. Both run a 6x4 electric prop, the slow fly type, just cheap ones off eBay. Get some model plywood to make spare firewalls as well, plus make up spare power pods for your TT. I have destroyed 18 pods in 3 months. Get a couple of 500-850mah 2s lipo packs and a charger, then you can fly.
The SE5 is not a beginner friendly flyer IMO, it’s hard to fly compared to the TT and is much more prone to wind and trim issues, don’t fly it until you have racked up plenty of hours on the trainer.