Welcome back.
Every week there is a 'is it worth it' thread started and here is my two-penneth.
I only have SH3 installed (obviously not stock!), SH4 is sitting on the shelf waiting for me to get bored with 3 and has been there for about six months with no signs of me dusting it off just yet - but (I've read) that the U-Boats mod
is definately worth it. SH5 is now so cheap it'd be daft not to get it and see what it's like for yourself, as there are so many for and against it can be the only way!
As for the supermods for all, you'd need to try them to find the one to your liking.
In the words of Dr Pepper - Try it, you might like it!
I look forward to your input in these forum when you get the chance.