Semi Slav is perhaps a very solid opening. I never tried so much but I have experience playing the Caro Kahn structure.
What should we do about White's e4 pawn break and how does the c8 light square bishop come into the game?, it doesn't do much on the b7 square stuck behind it's own pawns. Also if we move it too early say Bf5 and then e6, we will get hit with Qb3 stuff.
PS suggest some Good lines. Or exchange Slav is better?? (dxc4)
@SaberTooth1602 yes, the Semi-Slav is a well-regarded opening. Most of the questions you're asking relate to the Slav (without ...e6) rather than the Semi-Slav. In fact, the positions in the Slav are more likely to resemble your games on the black side of the Caro than those from the Semi-Slav (even though you will play ...c6 and ...e6 in many lines of the Caro).
Just be aware that despite closely resembling one another, the lines in the Slav and SS tend to be unique from one another -- it would be good to choose one or the other as they transpose more seldom than you would assume.
The best free introduction to Semi-Slav I know about is on Chessable: www.chessable.com/short-sweet-semi-slav/course/35319/
You cannot use it as a repertoire, many key lines are missing, but it is a great introduction, answering some of your questions above.
Exchange Slav is a term used for White's 1.d4 d5 2. c4 c6 3.cxd5. You cannot avoid it in Slav (dxc4), but you can avoid it in Semi-Slav via different move order (1.d4 d5 2. c4 e6 with c6 later, inviting Exchange QGD or even 1.d4 Nf6 2.c4 e6 and c6 later, inviting all sorts of stuff).
Both Slav and Semi-Slav have been used at Super GM level, I don't think that one is better than the other.
In my limited experience Slav seemed easier to play and Semi-Slav offered more chances for my opponents (and me) to go wrong in complicated positions.
In the end, the decision is yours.
All of them are playable.
The Semi-Slav is perhaps more ambitious. The seemingly bad bishop on b7 in the Meran, can easily become whites nightmare. It's not at all a french bishop.
With the regular Slav (1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.Nc3 dxc4 5.a4 Bf5 (Note that here 4...Bf5 is almost loosing for black)) you get more solid positions, similar to the London System, where all your pieces are getting to decent squares and you have no exploitable weaknesses but white is of course still better.
Depends what you want.
Aggressive players usually prefere the first.
Calmer ones the later.