Thanks for pointing out the R’ Avraham ben Harambam, you definitely can read אבל הכוונה להודיע בה מספר הגביעים וכפתורים והפרחים ומקומתם to be davka those, although I definitely would not say that the Rambam “says that the branches were straight”, at the most he implies it through a picture (even if that part of the picture was accurate.
(It would also make more sense for the Rambam to try to make the shape of the menorah in his picture as accurate as possible, as he is trying to show where the geviim were)
About the 2nd sefer you quoted, he says that מדברי הרמב”ם ורש”י הנ”ל ברור ועליל שקני המנורה ישרים, which, legabay the Rambam, is definitely not in his devarim, at least (from R’ Avraham ben Harambam it is, but that isn’t who he is quoting), and all that Rashi says is that it went out באלכסון, which doesn’t necessarily mean that it went in a straight diagonal line at all, just that it wasn’t flat.
Thanks