At 20k, the Jug has an advantage over the La7. The La7 is really only good up to maybe 12k, above that it is still VERY fast, but it loses a lot of its acceleration. Against a Tempest, well, you are screwed
.
Against the 109G10, the fight should be pretty even around 20k. If the 109 is BnZing, all you need to do is be very patient. Just make a fairly gentle break turn when you see him coming, and it he tried to track you, go into a barrel roll or another evasive. Eventually, you will wear down his E advantage (plus you will get snapshots every time you force him to overshoot). If you really have to get away from the 109, you can go into a dive. Get above 400 mph and then start doing some gentle turns- the 109 will be unable to match them because his controls won't be working so well at that speed. Once you get him to overshoot he is yours- the planes are just about equal in a 1v1 fight. Hopefully, some of the Jug experts can pop in and give a hand here, my advice is mostly from fighting them in the 109.