For freezing, you need to re-look at the freeze menu within Reaper. There's several different options and the one that I use allows for editing. All you have to do is click the "unlock" icon on the media files that got locked during freeze. If you select them all, you can unlock them all at the same time. You may need to enable the lock/unlock media item within the media preferences.
As for the optimizations, it would be nice to have an optimization guide but i think it would be very difficult to assemble since computer installations vary wildly and exponentially from computer to computer, OS to OS, preferences settings to preferences settings, Reaper versions to Reaper versions.
I find that for now, it's up to the user to do the research thoroughly to find out what optimizations work by reading a whole lot of forums and blogs and websites for pro audio and the like. Whenever I do this and learn something good that works, I share the results on forums like this and other forums so that it's easier for the next person(s).
Luckily, this forum is a lot more user-friendly than other forums and support sites. And the Reaper developers really do care about making Reaper work well. They really work hard and have for many years now, and it's paid off because Reaper really did get better.
A lot of other software really doesn't have all these advantages nor the good userbase.
But if I were you, I'd send an email to Cockos about your request and see what feedback they give you. Also, be sure to keep doing internet web searches for Reaper optimizations and tweaks and for keywords such as latency, and buffer and playback, etc. Sometimes internet search engines give better results than forum search engines.
The optimizations I learned were for my Linux system, but I think a lot of them if not most of them would be applicable to other systems. Search for posts by me and you should find a fairly recent post I made with my better settings. Sorry that I can't remember the exact location of the post. But I remember that I posted up the same info on
http://gearsz.com and on a particular Ubuntu Linux support site.
I wasn't sure which settings were absolute best, but I uploaded screenshots of my settings that finally worked best for me so far. I wrote in text explanations on the pictures and on the forums where I posted.
Good luck.