I have done both those routes several times.
From Great Harbor south your 4.1
draft requires high tide. The most shallow place is in the area of your 2nd to 4th waypoint. Go slow and look very carefully. In this area a small move port or starboard can make 0.5 foot difference, so noodle around if it gets tight. After that the channel is east to pick out. There is another thin place about your waypoints 9 and 10, but if you made it this far away this place is just a matter of reading the
water to stay in the narrow deeper part, easy. Pick high tide on a relatively calm day and give it a try. There are miles of shallow
water along here, great for getting in the water and swimming around.
On the second route, I’ll call it the backside of Hoffman’s is no problem at 4.1 but there are two places to be very careful. The first is when approaching Hoffman’s from the north looking for the turn to follow parallel to the shore. This area is a broad basin where again moving port or starboard might yield another 0.5 feet. Last time I went through here the deepest water was right over a large dark area ( might be grass) which was not intuitive from reading the water. The second place is when the channel approaches the shore after following parallel past about a third of Hoffman’s. There is plenty of water, but the deepest part runs quite close to the shoreline. Like less than a
boat length close. Go slow with the sun over
head and it will be easy.
With your draft you may find a number of great shallow
anchorages somewhat removed from the crowd.