Welcome!
From my limited experience (started using renoise last year)…
- Most tools should have a discussion link (linking to a thread about said tool) which not only allows you to find out a little more about the tool itself or even suggest/request more options with said tool, it gives you the opportunity to report any errors you may receive and for the developer a chance to rectify the problem. This system in my opinion makes it pretty reliable.
I have not had any problems with any tools so far and as best I can tell, people seem pretty good at responding to errors, I can safely say that the renoise community is the best related to a Daw i have ever come across.
- Maybe someone else may suggest some go to tools? I browsed the tools initially and added the ones I thought i may use, however, what I found was the more i dove into renoise, the more I began to have questions, the more i needed solutions to things i wanted to achieve. I posted my queries here and have been recommended tools that helped me to do what I wanted to do.
Having said that, here are some tools I am using that I find of great value:
Rubberband (Time stretch & Pitch shift):
http://www.renoise.com/tools/rubberband-timestretch-pitch-shift
Pattern editor find and replace (A tool for finding & replacing raw pattern data - notes, instruments, fx etc):
http://www.renoise.com/tools/patterneditor-find-and-replace
Slide to next note (Inserts slide effects that will slide to the next note in column from the current cursor position):
https://forum.renoise.com/t/new-tool-2-7-2-8-slide-to-next-note/34026
Batch adjust bit depth (Adjust the bit depth of all samples in the current instrument to 8, 16, 24 or 32 bits):
https://www.renoise.com/tools/batch-adjust-bit-depth
Note properties (gives you extra controls to manipulate the currently selected note and its properties):
http://www.renoise.com/tools/note-properties
Multi volumes (lets you control multiple track (pre&post) volumes and maintain their relative level):
http://www.renoise.com/tools/multi-volumes
Also of note which I am just getting into is The Cdp tool (Sound design tool):
https://forum.renoise.com/t/new-tool-3-0-cdp-lua-tool/41466
Some others may have a few more suggestions, I feel as though I am just scratching the surface.
Not sure about the flanger. Maybe someone else could weigh in on this?
I am also using PT11.
The support by the Renoise team and community is in my opinion and experience, better than any other I have come across 
Happy renoising!