This is pretty much what I've been looking for. I've been playing on and off for some months with cl_interp 0 and cl_updaterate 1000 or higher in order to achieve a lower interp, but whenever I set it higher than 66, jumping felt kinda harder, as if the timing window for syncs had to be more spot on and angles and timings on wallshots had to be very near perfect, pretty interesting to practice with actually, but I felt like it messed with my understanding of the physics or jumping mechanics. However I think that issue is gone with this command, physics feel the same, just with no rocket delay.
Perhaps these aren't very good settings because of the netcode, 66 ticks and whatnot, but I can say I really enjoy using it for jumping though. I assume if servers can(?) and already have this forced to 1, it's gonna be set to the standard 15.2 ms anyway? Also maybe this "feeling" is all just pure placebo on my part and there's no difference whatsoever, so take it with a grain of salt I suppose, and try it for yourself perhaps.
A small tweak people might like as well is snd_mixahead 0.045, default is set at 0.1 and custom cfgs might already have this implemented, it essentially lowers the general(?) sound delay, results may vary though so try different values for yourself like 0.04 or 0.05 or higher. I find that if I go lower than 0.04, the audio really starts to mess up unfortunately.
A too low interp (lerp ingame) causes lags and / or fps drops.
I'm not sure I've ever had that issue, however I can definitely say that I sometimes get stutters or microstutters, though I think this might just be source engine in general being a bit wonky. e.g. on jumps that grant you overheal, stuttering becomes a lot more visible and for some magical reason this can be avoided with net_fakelag 0.001 or whatever value, and it feels so much smoother. The only downside is the fake lag, which doesn't even feel like actual lag, but more like a sort of slow motion feeling.
Sorry if I derailed the thread a bit.