I will second that you need to look at each mfg's specs on club length and lie with the club you got fitting with.
For example Callaway Apex 5 iron is 24* and 38", XR 5 is 23* and 38.25" and XR OS 5 is 25* and 38.5". I'm sure there are slight lie differences, +1/2" doesn't seem a definitive length.
I've had 4 rounds with no double bogeys in the past 2 years, and I've broken 80 3 times in that same time. So, equally hard for me, I guess? In 2 of those 4 rounds, I had at least one triple bogey, though. So if the question is it is harder to break 80 or not have anything worse than a bogey on your scorecard, then I'd say the latter.
In general, I don't try to be precise enough to control the distance to within more than 10 yards on an approach shot. So, the answer is nothing. For example, if the pin is at 120 and the center of the green is 125, I'm hitting my 125 club instead of trying to adjust my 125 club to go 120. If that club goes anywhere between 120-130, that's totally fine by me. If I tried to hit that club 120, the odds are still that I'm not going to have a close putt, so what's the point? Aim at the center of the green, 2 putt for par, and get out of there.
That said, if I really need to control my distance (say I'm pressing for birdies in a tournament or playing a scramble), I have a couple of techniques:
1/2 and 3/4 swings with wedges. I'm not going to bother with this with anything above a pitching wedge, because we're not precise enough with longer clubs to invest time into learning those distances.
Grip down a little bit. That will take maybe 5 yards off a club. Hard to know that for sure, because I do that once every 5 rounds or something.
Flight a club like this (I use this technique more when I don't want a lot of spin with my wedges):
I think trying to control distances on the range is a fun brain plasticity exercise or a good break from working on your priority piece. Nice to be able to pull out when absolutely necessary. Sort of like hitting a big slice or big hook.
Breaking 80 is tougher, I believe. Although I haven't technically crossed the threshold so maybe my opinion isn't valid.
I'm not tracking my handicap, but I have been shooting mid-eighties lately from the standard men's tees (6,100-6,300 yards), consistently now for a while. The piece of my game that is consistently dragging my score down the most right now (for a while now) are penalties. Those 2 strokes at a time freaking KILL my score.
With that being said, with a penalty and my current playing ability almost assuredly results in a double-bogey or worse. But I can still shoot an ~85 with a couple double's or one of them a triple in there. I'm shooting a lot of pars now. I VERY rarely get a birdie. For some reason I cannot reach par 5's in 2 and they aren't particularly long on my home course. I think I've had 1 birdie in my last 3-4 rounds? But I can tell you, when I have ONE birdie on my scorecard it is usually HUGE to my score, and that's when I'll usually have a < 82-84 day. Something about getting that birdie on the scorecard makes my confidence grow.