From you question I gather that you are planning to do your trip in June. By then the waters of the Chesapeake should have warmed significantly. That will remove much of the danger of the 7 mile open water crossing from Crisfield to Tangier. That said, this crossing is the most exposed and thereby dangerous portion of the Chesapeake Bay. It is on the northern end of the widest place in the bay and has the longest fetch of any part in the entire system. During bad weather this particular place can get rougher than any other part of the generally protected waters of the Chesapeake. Our region is on of the least complicated and safest areas to paddle in the world.
You also did not mention whether anyone else, particularly anyone with experience, will be accompanying you. Alone is always more dangerous than traveling with another experienced person.
If the weather forecast is benign, then I think that even an inexperienced person in good shape and with superior attitude can make that trip. If the weather turns nasty it could be problem. That said it certainly does not compare to flying an F-22 into a hot zone, so danger is relative, is it not? But the more prepared and trained you are the more danger you can handle should it arise. Paddling to Tangier as your first expedition is ambitious.
Remember that there are alternatives to paddling over to Tangier. The ferries out of Crisfield will take a kayak and passenger over to the islands, so you can always avail yourself of those services either from the get go, or if the weather on your chosen days is bad, either coming or going.
As another alternative in that same area that will give you the same scenery as the Tangier islands, you could follow the water trails at Janes Island State Park just north of Crisfield. They are closer to shore and thereby much less exposed.
In the trip reports on the site, you will find stories Janes Island and the Pocomoke as well as the one you mentioned on Tangier/ Smith Island.
Another thing to keep in mind is that June is still early in the nesting season for shore birds and camping on the small island spits between Smith and tangier can be disruptive to the nesting birds there.
River travel is always much more safe than exposed places like Tangier. the Pocomoke is unbelievably beautiful place and I recommend it to you highly.
The northern Chesapeake is much different than the southern bay. The wide variety of land forms and environment available to us on the Chesapeake is one of the best things about this place. So many different things to see in a relatively small place.
There are many paddles described on the site for the northern Chesapeake, quite a few out of nearby Havre de Grace. The Bohemia, Sassafras and Chester Rivers are all interesting places to paddle and easily drivable in an hour or so from our mutual hometown of Bel Air.
As to what kind of boat to get that is like asking another person what kind of woman to go out with. Everyone has a different need and a different opinion. That is a good thing as if we all like the same thing it would be impossibly difficult to get.
All I would advise you is that it is best to try a bunch of different ones before you settle on a specific one. With kayaks this is a rather easy thing as there are many places to rent them. I would rent for a good while and then see if I could find a used boat that meets your needs.
As far as a boat for the Chesapeake, you don't want a real long straight boat as they are difficult to turn in the many small creeks and marshes you will want to use it in. Then again you don;t want anything too short otherwise it will be hard to use when you want to make that crossing out to Tangier. If you want to camp from it you need to make sure it has enough volume to store your camping kit. Most kayakers do not camp and are not interested in boats that can handle gear. Therefore most boats are too low volume to make for good campers. Pay particular attention to the clearance of the hatch openings. Some boats like the Necky Chatham are great performers point to point and day paddling but useless for camping as they hold almost nothing.
On the Chesapeake Bay there is little worry about surf, but if you think you are going to use it on the Atlantic side like Assateague, Delaware or Virginia Shores, then don't forget that boats with really pointed bows look sexy and go through waves really well which seems desirable. But they also go down into a wave really well which isn't so good when you are sliding down the front of one on your way into the beach.
So any boat you buy will be a compromise between properties as no boat does everything the best.
Good luck and hope to see you on the Bay this summer.