Timestretch Question

Is it possible to easily stretch loops without affecting the pitch within Renoise?
Or should I use a vst for that

Also how easy is it to record and edit modulation in vst’s?
I’d like to know before I get the full version.

If you mean have those kind of features been natively added into 2.5 yet? No, not yet, you will have to use a VST’s for that.
If you want to feel how easy it is to record and edit modulation in Renoise i can only recommend you to try the 2.1 Demo in that regard. The demo has limitations on only three areas: ReWire crippled, no WAV rendering to disk and to instrument, no ASIO support. For the rest you can produce and use anything else inside Renoise including all remaining save and load features.

There might be one noticable difference between 2.1 and 2.5:the audio engine in 2.5 uses a quite some less CPU resources than 2.1