I tend to wear compression tights in winter for most of my runs, whether long or short. I have run 3 or 4 ultras in them which were in February/March time or in September so never had a problem with over heating. I'm not sure what I would do if racing in a warmer month. The tights are relatively thin and breathable so shouldn't cause too much problem on a warmer day. In warm weather, I would focus more on what I wear on my top half as that is where I would feel warm.
I have both Skins and 2XU and prefer 2XU. Although I should say that my Skins are 5 or 6 years old and I suspect they have evolved since then.
There is much debate about whether or not compression tights make a difference to your performance and recovery. I believe they do but not enough to deal with ITB issues. I believe they keep your legs feeling slightly fresher for longer.
Plenty of discussion on here about compression tights. I had acupuncture when I suffered from ITB problems and plenty of good stretching should help. Good luck with your injury.
Also have a look at Inov-8 as they do some good packs.
I ran a couple of Ultras with an Inov-8 and whilst a good pack, I wanted to know how much fluid I had left which is very tricky if using a bladder. I opted for a bottle system and went for an UltrAsprie Kinetic vest. Fantastic bit of kit for a 50k. Well worth a look.
I run in compression tights when the weather gets a bit colder or when I'm doing longer runs (from 15 miles up to 50k). I bought them originally for the longer runs but found them more comfortable on short winter runs than cold legs. Also have an old pair of Skins I wear for recovery after a long race.
Personally I think they reduce muscle fatigue whilst running but the amount isn't that much. I have read the arguments for anf against compression gear but I like them. Never bothered with compression tops though.