100 miles isn’t a lot of riding so you may get used to it but I do find I get a strong intuitive idea very early o about whether a bike feels right or not.
Road bike feel matters in particular as you tend to stay in the position for hours on end.
A few considerations you might want to play around with:
1. Saddle position – fore and aft
2. Position of the brake levers on the bar – forward and back and even in and out
3. Stem height
4. Stem length
5. Stem rise/drop
6. Bars – some drops have more depth (up and down) and reach forward than others. There’s also bar rotation
I recently decided my 120mm Thomson Road Stem was too long despite having had it for 6 years, tried a 110mm Cinelli but the angle was too high, then a 120mm Cinelli which felt still too high and ended up with a 110mm Thomson – a right palaver if you’re a bit picky like I am (!) but it shows how much tiny adjustments can make on a road bike.
Worth paying for a bike fit IMO if you’ve not had one before. They can save you a fortune on faffing about with new stems and bars or physio bills