NOTE: many of these stats, hypotheticals, graphs, etc. are assuming Little Rock and UT-Arlington leave the league as has been reported . Map...
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Some highlights:
Football
The expanded Sun Belt will be a step up in football competition from Conference USA. Current C-USA's 4-year FPI average (2017-20) + incomplete 2021 results (2017-20) is 100 --- bottom of FBS. A Sun Belt with USM, Marshall, JMU, and Old Dominion is 3rd in the G5 behind the AAC and MWC and within striking distance of both for top conference in the G5. The Sun Belt has done a good job in producing elite G5 teams despite the lack of a NY6 bowl appearance in the conference. 6 Sun Belt teams (App x3, ULL x2, Coastal x1) have finished top 45 nationally in FPI since 2018 while C-USA has had none in that span. Coastal and App State are in position to finish in the top 45 in 2021.
So, initially, the East will be the tougher of the two divisions by a bit. The 2017-21 average of the East is 86.3 compared to the west having an average of 100.1. 4 of the top 5 programs from 2017-21 will be in the East while 3 of the bottom 4 programs will be in the West. This spreadsheet also supports the idea that James Madison can be competitive immediately. Couple this with quality facilities, a robust budget, and good fan support (they'd be top 3-4 in football attendance in the new league at 23,000+), you see why they were added.
Basketball
C-USA 3.0 was a 1-bid league every year and this will be the case in an expanded Sun Belt unless one team were to put together a gaudy profile and land an at-large bid. The 4-year KenPom average (2018-2021) in C-USA is 0.08 --- i.e. a very slightly above average D1 conference. The 4-year KenPom average in Sun Belt without Little Rock and UT-Arlington and with Southern Miss, Marshall, ODU, and JMU is -1.79 --- a slightly below average D1 conference. But the reality is both are one bid conferences. The new Sun Belt will just be a touch easier one than C-USA in current form.
Budget
Here is the USA TODAY budget link for 2020:
https://sports.usatoday.com/ncaa/finances