A fill-to-fit option would be a welcomed feature. Suggest it.
Perhaps the best way to accomplish the task is to do a little math. Jump the cursor to the end of the gap and note the Cursor time. 
Jump to the start of the gap and subtract that time from the end time.
Right-click the clip to be sped up and Change Clip Speed. Click the Duration field and input the time that you calculated.
The sped-up clip is then the same size of the gap. Leave it on track 2 and it will override the gap.
Using v10.48 couldn't replicate your post-speed add-effect complaint...
Sped up three clips on track two, selected them, then added several effects. Result was three sped-up clips with effects.