The PT or OT at your clinic should write up some specs for the DME. Then your assessment should be in your home so the DME rep can see the lawn, etc. Probably a bumpy lawn suggests a mid-wheel chair but there are several factors so you want to make sure all the things you want to do in your chair are clear to the ATP.
If you use the search function here and elsewhere, you can find a lot of good information on power wheelchairs, though some is more personal preference than science.
If there is more than one DME (equipment firm) in your insurance network, I would keep an open mind about which one may suit you best, regardless of which one your clinic recommends. You can switch midstream if necessary, though of course that slows things down.
Most PALS do best in Permobil chairs. You should be able to drive a loaner or test drive one at the DME's offices. A matrix of their current models so you can check them out is
here.
This page lists some other resources that you may find helpful.
Medicare should cover tilt, recline, seat elevation and power foot/leg rests. I would also ask about arm troughs and alternative drive controls. Sometimes these are ordered with the chair and added when you need them, since it is harder to get anything approved for the wheelchair after the initial order.
A case can be made for anterior tilt (Active Reach) and I would ask that be included as well. It may be denied initially, so the order should include the appropriate justification (you still have some upper body function and live alone).
You should ask that a ROHO seat cushion be included if they do not bring it up. In fact, you should approve the spreadsheet that is sent to the insurance company for approval to make sure nothing is left out. The dimensions of the chair itself may be important to you since you are using transit and may have narrow entrances at home, so you want to make sure when they measure your body that they are precise.
You also need a safe, comfortable postural support (hip belt or chest harness) on transit; I always recommend that the Bodypoint brand be specified (I used to work there, but they are still the only standards-tested line).
Some of this stuff may annoy the DME. That's one of the benchmarks of a good vs. bad DME -- the one who's less annoyed. If your network includes out of state providers, you do not have to stay in state, but since wheelchairs do need tweaking, especially on delivery, you would want a location that you can get to -- in-home/in-clinic service is less a thing these days with staff shortages.
Documentation at some DMEs is not all that. Keep saying "ALS" and if necessary "terminal disease" to everyone you talk with. Everyone in the supply chain is supposed to prioritize those. If you are working with a care manager at your local ALS charity or a case manager with your insurance plan, they may be able to help grease the wheels to get things done as well. Some orders go smoothly, others not so much.
It's important to keep pressure on if needed because no one has enough parts or resources so sometimes you have to be the squeaky wheel. It used to be pretty reliable that PALS got their chairs within a month or so of insurance approval -- now, that approval may take longer and the post-order interval may be longer as well.