Is there a quick method to cut the excess clip off the Editor Timeline after increasing the playback speed? Also, would it not make sense for this to happen automatically?
If you are talking about the Speed Effect, no.
The Speed Effect IS an effect. This means it comes after frame range, and Masks.
Placing a clip defines an absolute range of frames. Then the Speed Effect alters playback of those frames. Problem is, trimming the clip shortens the frame range... Speed applies AFTER the frame range is defined. You just lost frames off your effect.
Bake in the effect--Convert clips with Speed into Composite Shots (move the effect into the Comp), then you can trim the clip on the Editor Timeline.
Use Rate Stretch. Rate Stretch is applied before effects.
Change FPS in Media Properties. This is applied before Rate Stretch! Knowing order of operations is important.
Speed Effect should pretty much only be used for speed ramps.
I set the speed/duration to 150%. I need to specify an exact amount (so I can't use the rate-stretch tool) so I can adjust all the timings in a composite which I made to go along with the clips. I can't just adjust the speed/duration of the whole composite because that would affect also the duration of certain animations which must remain the same, even if they become more dense).
You can specify an exact amount with the Rate Stretch Tool. Right Click> Speed/Duration, I think.