I'll second what Janice said. Hermit is an ass-kicking trail. Very steep sections in the upper areas, steep with big steps down and sections of cobblestone. If you're carrying 30+ lbs, this will impact your feet and knees pretty good. Then you have to descend the Cathedral stairs, which I recall being very steep again. When I last successfully did it, we camped at Hermit Creek, which was about 7 miles. We were beat!
Going to Granite just adds more miles. Don't let the Tonto fool you, it's not flat. While it's better than any GC assent or descent, it still should not be considered an easy stroll. Also the Tonto has very little shade, so that takes a toll on you as well.
Also consider the temps at the Tonto and lower elevations and when you'd be hitting the devils staircase on Bright Angel. I'm in Phoenix and the temps were in the upper 90's today. Tonto and lower can get to those temps and much higher, so be very careful.
Also consider the time needed to filter water. Filtering the Colorado is not fun. Filtering Monument creek should be fine. Don't rely on anything else unless the Rangers tell you differently. Havasupai Gardens will be your next stop for water.
If you're not familiar with the GC or desert hiking, this is not the hike to get familiar.
20 years ago, I did Hermit TH to Hermit Creek, then next day to Granite Rapids, then next day to Horn Creek, finally last day hiked out via Bright Angel. Those four days were both the hardest and best GC hike I've done, but I vowed never to Hermit again.
In October 2021, now being 50, I decided to give it a try again. I made the smart decision for me to turn around before Santa Maria springs because the weather at the elevation was approaching 90 in the morning and everyone I passed coming up said the inner gorge and Indian Gardens was 110-115 degrees.
We don't know your fitness and experience level, but I'd recommend caution.