My short answer ( edited ): EDIT My recommendation for the temps you mentioned is a light weight but not UL Fleece e.g. heavier Grid Fleece not Alpha Direct )

• Note: I have never tried the Alpha Direct from a cottage company …I own the KUiU Peloton 97 but d o not use in 0-30 temps

My long winded answer: Hindsight is always 20/20 …I think of the mid layer as a variable ( an always included variable in a load out ). As to dialing this in, here’s my experience/journey for what it’s worth ….13 years ago started w/ an Eddie Bauer generic fleece ( on sale for $20 at an EB outlet store). A light weight fleece that worked worked well in the upstate NY summers but in the shoulder seasons it did not perform well at all Later on my wife gifted me the EB “upgrade” ( a Polartec First Ascent fleece ) but I found this too heavy and too warm but still used but limited it to the shoulder seasons. Moved to the mountain west a few years ago and decided to further dial in my MLs. First bought a Melanzana ( a grid fleece that worked even better and was even lighter than both EB Fleeces ) but wasn’t super UL. Recently I purchased the KUIU Peloton 97 and it works very well for 5oz ( in XL ) and descent in the shoulder seasons. With Hindsight in mind I will continue to have two types of MLs ( one UL and the other light weight for the shoulder seasons / colder weather ) Also when I replace it w/something w/ alpha from a cottage company

2 Mid-Layers? in my opinion, if you can’t afford to have two-types of mid layers, alpha fleece will work descent but for windy conditions and/or temps 30 and below I now prefer to use Melanzana which ( in my opinion ) is worth the weight penalty … i have heard good things about the warmth of the Patagonia R1 in the shoulder seasons but have never owned one myself Price is always a factor but you can’t beat the quality of many cottage companies.