They may require you to use their services, but they may not be as picky about whether the plan was their production or not.

George Washington acquired a significant amount of land this way, and shortly after acquiring such created SYNDICATIONS (he later used JOINT STOCK COMPANIES when they came into existence) to raise the capital needed for development.  

I have a 2 bedroom 1 bath in highly sought after Judson Mill area of downtown Greenville, but haven't decided what I'm doing with it yet as I have several other projects going on right now.Most of my rental portfolio has been acquired from tax lien sales.

It's not the cheapest yet their price were not that much more than their competitors and SIW was a better product.

If I acquire the second property with full cash, that's at least an instant equity which I may be able to tap into for 3rd, 4th,..assuming properties rise in value over time. 

I have a RE LLC with each property in an RPT.I own 3 LTR SFHs in North FL that I acquired pre/during-COVID.

Are there other software products out there? 

I am on the journey to acquiring a charming 2-bedroom, 1-bath cottage in a popular tourist area.

Lendio shut down it's accounting product "Sunrise". 

If you're building one at a time and one of the big monster production builders needs work done from your #1 go to, you need a backup plan, and a backup plan to that backup plan.#3.