So you are completely new to FMQ?
From what I have observed, most people prefer a frame setup to a sitdown. For those who opt for a sitdown machine, it's often because (1) they don't have the space for a frame, (2) they have physical limitations that make standing at a frame uncomfortable, and/or (3) they have already done a lot of FMQ on their domestic machine and want to stay with that method. Just in general, most people find it easier to move the machine (like a pencil on paper) than to move the quilt (moving the paper under the pencil). There are always exceptions, but if you were basing a choice solely on probabilities the probability is that you would prefer a frame setup.
Do you have enough space for a frame? That is most often the limiting factor. The space a frame takes up is often underestimated. I have a 10' frame, which equates to 120". I can easily quilt a 100" wide quilt, not quite so easily a 105" quilt. I could maybe do a 110" quilt if I am willing to use just one side of the frame for changing the bobbin, although that makes it pretty difficult to put side tensioners on the quilt. It is possible to do part of a quilt and then reload to do the borders (or the bottom half); however, it's enough extra work that quilters do not want to do this unless they have no other choice. I personally would not consider 88" to be able to comfortably handle a queen-size quilt unless the quilt has a fairly small drop on the sides. See this website that gives both mattress top dimensions and typical quilt sizes for specific mattresses:
https://www.quiltingcompany.com/sugg...hm-welcome-new
In terms of a frame, you need to be realistic about how much space it takes up. You need to be able to get around at least one side of the frame (and it's better to be able to walk around either side). In my lithe days, I might have been able to get away with 2' on a side. Now 3' is much better, and 4' would be paradise. In terms of width, my 10' frame really requires a minimum of 14'. People also often underestimate the depth of the frame. My frame is about 40" deep without the belly bar extended, an additional 14" with the belly bar up. Aside from the machine depth, you need a minimum of 3' to move around in front of the frame, and an additional minimum of 3' if you want to be able to do pantographs from the back of the machine. Minimum space for my 10' frame is about 14' x 12' to be able to comfortably access everything, and that is a little on the claustrophobic side. A bigger space is always going to be better.
If at all possible, you want to buy the machine and frame together. As a beginner, there are many mistakes you can make if you don't do this. Plus, it's just easier to know the machine and frame are compatible from the get-go. Saves a lot of time and anguish.
What is your budget? The midarm setup I have (Voyager 17 with Hinterberg frame) can often be purchased used for $2,500 to $3,500. While not perfect (the Innova is my dream machine), it fulfills all my basic needs and is a good starter setup. Have you checked out the Block Rockit? It gets very good reviews, and I'm sure there are some other entry-level setups now that don't cost an arm and a leg. Depending on budget, you may want to purchase used as you can often get considerably more for your money that way.
Regarding stitch regulators, some are outstanding (such as Innova) but others leave much to be desired (such as my Voyager regulator). If you can't get a really good stitch regulator, then my advice is to not use one. In my opinion, this is not a make-or-break consideration whereas space really is a make-or-break.
Edit: Here is a link to the Block Rockit:
http://www.kathyquilts.com/blockrockit/