Snap is a work in progress. Remember, 7.5 is beta. The audio slider bug has already been reported.
On the isolation issue, here an isolated clip retains the left edge position whether its left handle is dragged right or the right handle is dragged left. I.O.W., the leading edge of the clip is static, no matter how it's sized. This strikes me as being the correct behavior. But <alt> will overcome it if it's not the result you prefer. Hopefully, the drop-down menu issue soon will be remedied.
As for delays, test both states of the Use Hardware Acceleration checkbox in OPTIONS||EDITING tab. And yes, a higher-end CPU may help. Be sure that the video driver and Direct-X are up-to-date. https://www.nchsoftware.com/videopad/kb/1772.html
Submit a project that lags and someone will check it against their PC.
Here's how... http://nch.invisionzone.com/topic/23659-tips-for-getting-help-on-this-forum/
If it contains sensitive material you can link it in a personal message (PM) to me, via the envelope above. Be sure to FILE|SAVE PORTABLE PROJECT AS, not simply SAVE PROJECT, and don't forget to share it.
While these issues are vexing, personal experience demonstrates that programmers for NCH are more responsive than are those for some other companies. Two cases that come to mind are certain legacy features that were broken with the advent of Windows 8. It was years before they were corrected, despite the fact that a simple fix for one failure was published early on in MS support groups. Recently, a broken critical app in a popular Android emulator took six-months to fix.
When you spot problems not discussed above please begin a new thread with a descriptive subject.