I tend to pinpoint the anaerobic threshold (FTP) at 88-91 percent of max HR, though it varies. I held 93 percent of max HR for 68 minutes once in a half marathon.
Aerobic threshold, which is more like "tempo" or "sweet spot" in cycling, is closer to 80-85 percent max HR. That's like "marathon pace" for runners or a wattage that could be held for 90-180 minutes for cyclists.
This is basically what you do when you're pulling in a breakaway in a 3-5-hour flattish stage. Then you go back in the wheels and let your power and HR drop for a sec, then pull again. If you are solo going for a long raid, you ride at 90-100 percent of this wattage on flats (you need to do more power on climbs) depending on how long you have to be off the front. Remco is really good at this, incidentally.
Also, this is the pace ridden on most of the longer climbs for the top GC riders. For example, you might have a Grand Tour queen stage with a 30-minute climb, a 45-minute climb, then a 30-minute climb. Unless there is a battle plan, the domestiques are only going to be able to ride the first two climbs at what is a tempo effort for their team leaders (say 5.2-5.8 w/kg) and then the GC riders will race the final climb at closer to their FTP (6+ w/kg) with only a couple domestiques left. Remco hasn't shown the ability to excel in these monster repeated efforts, even though his one-off efforts are probably right up there with the Slovenians.
Most of the climbs in Itzulia are shorter and will be ridden closer to 95-110 percent of FTP, I would imagine. Repeating those efforts is the challenge for Remco.