200 max is not unusual at all, don't see reason for discussion. As for easy running, I used to run slowly + make hard workouts, also at the initial stage I walk, not even ran long slow base in the low-HR zone. I thought this approach was right. But you need to add something to progress. I met with one coach who agitates for intensity. He thinks that "LSD" running is useless if not harmful (psychology, nervous and immunity systems) even for novices, so they should focus on high-aerobic running. For 9 months he coaches some hamster who maybe similar to me. Slightly younger than I, he has no fitness expect some endurance, has no running talent if you not consider slow-twitch as a talent (200m PR 28-29 sec like mine). That hamster ran slowly and not so consistently and had PR for 5k about 6:00 mile pace. Now he is aiming for pace 5:35 for 5k, run no more than 45 mpw but with pace no slower than 7:10. Also Steve Magness writes that high-aerobic running, i.e. from slightly slower than marathon and half-marathon pace, is a best way to develop general endurance. Personally I rarely ran classic tempo or sub-tempo. Even for marathon I never ran half-marathon with more or less demanding pace, I made intervals, long easy run with 1:30 easy and 20 min fast, 10k fast, workout with alternate pace like 10k / moderate fast. According to Steve Magness slow-twitched runner must rely on his strengths: relatively fast and/or long running. Also if you slow-twitched than your easy running may be relatively fast and long. So my idea is to make 6:10-6:20 pace persistent gradually. Certainly not for every non-hard workout but it has to be at least occasional. I know although that some runners with 1:03 half-marathon rely on few hard workouts and do others almost as slow as mine by feel.