If the freedom of travel vs. pre-planned, train-specific sets of tickets is of any value in itself for you, that is already a good reason for obtaining one. Even a few flexible tickets might cost that much more - and would still leave less choices for making, for example, route alterations.
Also, a rover gives a wide latitude to change plans mid-way. One notable change for me was while walking along unbelievably gusty Portsmouth seaside promenade in the morning, having originally planned to go straight to the dockyard and then take a midday train to London. That was changed as I heard the noise of Isle of Wight hovercraft while crossing a seaside park! A quick inspiration of hovercraft+1938 Stock+steam line went through my mind and soon I was in the hover-harbour ticketing office, going through maps and timetables and planning my
ex-tempore diversion (and a thoroughly enjoyable one too) to Wight. In the end, I took only an afternoon train after the dockyard visit, but with a fixed ticket all this opportunity to change plans at a moment's notice would have been lost.
Another example, in terms of routing, of once changing a pre-planned route from West country northward from via Birmingham to via Newport and eastern Wales just at a whim of looking at a wall map in a ticketing office...

A fine walk within the jumble of Newport townscape while waiting for a connection and an unhurried clanking through countryside in a packed two-car unit...
secondaly I'm just wondering from anyones experience how feasable is it to go round with a tent and just plan it so i finish at stations next to somewhere to pitch up? Or is that asking too much?
If you are fit enough to carry it along with sleeping bag and other stuff the whole time

. Must also depend on your destinations - its usefulness might be lost in urban sprawl. There might be affordable (not necessarily the same thing as cosy or enjoyable

) B&Bs around, or you could make the Rover pay and use overnight trains as someone suggested.
Also which is better to get, can i do enough in 7 days?
Depends on the scope of the travel and "time-on-target". You could spent the whole seven days in traversing railway structures (and modern architecture

) in Gr'r Manchester area or around Glasgow/Edinburgh area - or you could make two dashes up and down coastal lines (with Forth and Tay bridges, of course) in two days, like me.

But Dundee was an unexpectedly interesting place, moreover...