In the language resource association panel a sort order is established:
Default sort order is alphabetically according to resource-name
The order can be changed manually.
The sort order is used for pre-translation: All assigned match-resources are searched. If there are found several 100%, 101% ord 103%-matches within different TMs, the one with the better sort order is taken. And within one match resource the match that is the youngest. The same match result order will be respected in the match result panel of the editor while translating.
Always only the best match is counted for a segment, even if there are multiple 100%-matches across resources.
In the language resource association panel it will be possible to assign a penalty for all matches from this resource for the current task
Note for Developers:
Also check implementation for LanguageResources from Plugins.