I am a many decades long hard shell kayaker. As a result of a horrific accident I am out of hard shells and into IK's.
For what it is worth, what I have found out.
The ThrillSeeker by Custom Inflatables, Inc. | Ready to give you the ride of your life!
was my first IK. Custom fit. As a long time squirt boater, If it works for the Snyder Bros, I figured it would work for me. And it did. Knowing I would do some self support I got a larger build than Attila recommended and it has worked great for me. Not a hard shell kayak but the closest IK I have found to a hard shell. It surfs really well and handles really well.
Next, I got a solo Aire Outfitter. Super comfy, runs class 3 and makes it easy altho seems to ride up and over holes whereas for me a least some hard shells seem to punch thru. Being mostly a creek boater, the Outfitter paddles a lot like my big creek kayaks did. Not as fast as a hard shell and the IK's need to be positioned a bit ahead of your target - but a great IK for me.
Now have a Aire Outfitter Tandem. Altho I have done a couple 4 day self supports in the ThrillSeeker, I think the larger Outfitter Tandem is gonna give me solo self support comfortable (like cold brews in my RTIC fabric cooler) and the opportunity to do some reasonable WW tandem paddling since I enjoy tandem in canoes.
For me the right sized ThrillSeeker would be my boat if I could only have one. I suspect the Tandem Outfitter would be the best boat for you if you could only have one boat. Think about the next paragraph before you think you can only have one boat that is perfect for every river.
My opinion, there is no such thing as a boat that can do everything just right. For me having the best IK for every thing means the three boats I mentioned above. Every one is different and you have to do your research and buy what you think works for you. Then try them out and hope you made the right choice, if not save your money and buy something else.