Hello everyone, first time on the thread and im not sure if this is the right one but let's go with it for now. I have a pretty spread out multibuild with 1lvl barb for rage. 2lvl fighter for unarmed fighting UA and action surge and the rest of the way monk with monastery being Astral self UA. Race is a tortle and im planning to max str and get the sentinel feat, its all cleared with the dm but was wondering how it would sound to others.

Sounds very MAD. Most of your monk features require no armour so you need dex for A.C.. Wis and con are both also important, especially the one that you use for unarmoured defence and you want to max out strength.  Rage will help against weapon damage but not other types.  You can probably make it work ok if you have a character concept that you want to play but if you are trying to build a super powerful character it probably will fail.

I agree with Jegpeg. Action Surge is awesome, but so are many other things. I would personally recommend a three level dip for Variant Ranger instead of Barbarian and Fighter. They can also take the unarmed fighting style, and with Favored Foe and the fact that Monk and Ranger are both Dex/Wis/con classes it meshes well. And many of the subclasses would fit well too.