The test you are describing is in principle right. However, it turns out that PMS runs in practice a policy which tends to always be a little more conservative in order to be on the safe side.
1080p is no problem. 4320p - which is not yet existing - would also be no problem per se. It is finer details that are decisive. Your files may have streams encoded in the high end audio formats which your TV can not handle. Or they have a video stream of excessive high bitrate or are encoded using sophisticated features which did not yet exist when your TV set was build. Subtitles also often create problems.
I do not want to leave the impression that the problems are overwhelming or myriad. But using a rasPi demands a little bit more planning when preparing the data. In any case you can convert (i.e. “optimize”) the data offline and make them that way available to be watched later on your TV set.
To be a little more practical. Why don’t you what on your present set up with the MacBook as server, whether your media need to be transcoded or not. Go to “Status” -> “Now playing” and hover over the image shown.