[jwyss234]

For accessory storage, you might try poly zip bags. Polypropylene is safe for plastic figures and paper and is used in archiving. Here's a link to a One Per Case post discussing their uses, where to buy, and sizes that work best. Some people don't recommend keeping figures in air tight bags so you may want to buy some with a vent hole or refrain from zipping the bag up all the way.

One Per Case: PSA: How to Store Action Figures Like a Boss

If you're need to straighten any accessories, you should be able to heat them up and they will return to the original form or close to it. Many people will recommend using hot water but if you have a lot of accessories to work on, it would probably be quicker and easier to use a hair dryer. 30 seconds to a minute should be enough.

For TMNT resources, you can try this site: The Virtual Ninja Turtle Museum

It doesn't have scale info, but it might help you figure out which accessories go with each figure. One important thing to remember with vintage TMNT, the later figures often had accessories made in different colors of plastic. For example, I have the Coil Force Raph and he came with pink weapons but the Coil Force Raph pictured on the site shows blue weapons.

For Transformers, I would suggest Seibertron.com and TFWiki. These sites are pretty good sources of information but you will have to do some digging to find what you want.
https://www.seibertron.com
https://tfwiki.net/wiki/Main_Page

Seibertron has lots of galleries for all of the Transformers lines. As you scroll down the main page, you should see a section called Transformers Galleries with a few of the newest galleries profiled. You should see a link near the title to View All of the galleries. From there, you can filter the galleries down to a specific line such as Generation 1 or Generation 2. You could also search for a specific character.

For TFWiki, use the search bar is on the left side of the site. You can search for specific characters or toy lines. Because Transformers has numerous continuities and toy lines, your searches will most likely route you to a webpage that will give you several options to help you navigate to the info you want. For example, if you search for Generation 1, you'll be taken to a page giving you options to view info on the cartoon, the American toy line, the European toy line, the comics, etc.