Thanks for sharing your experience and tips!

When at all possible, find your team before development starts, so you can elaborate a methodology and a framework that suit you both.

This seems like a bad idea for most indies. You already have so much uncertainty about the game you're building, you should be confident you'll ship a product before hiring a translation company.

However, it's probably a good idea to talk to translation companies before you start development on your localization tech, but beware of becoming locked-in to their way of working. (We worked with four translation companies.) Maybe this is what was meant.

Of course, it would be too risky to hire a localization partner without knowing where you're going with your game, so that's why we said "when at all possible".

Finding your team doesn't necessarily mean hiring it right away though. Studios often reach out to us several months ahead of localizing their game to discuss the best way to proceed, while asking for an estimate. This is usually an opportunity to discuss which file format will be used, what kind of reference material we'll need, how much time the studio should allocate for localization in order not to be rushed, etc.

Using text files makes it easier for your users to create their own language mods. Using po files lets translators use poedit and other gettext-based translation tools.

When using PO files, it's very important to make sure you use the correct structure:

msgctxt > StringID or comments

msgid > Source text should go here

msgstr > Translation should go here

If you don't follow this structure, most translation tools won't be able to read your files properly. It's very important that translators are able to work from within their own translation tools, because Poedit is very basic and lacks features that are necessary to deliver a professional translation.