Question #1: do you really need to remove your seal pelt to Shift 

Well it depends on what kind of "Shift" you are talking about. There is a shift of the mind and a physical shift.

1) Shift of the mind: A Glamour:

The shift of the mind is a shift that most Fae can do, which is to cast a glamor upon one's self and "appear" in a different form. 

2) Physical Shift:

A physical shift is more tedious and painful. To strip off the outer layer as well as to change the inner layer and shapeshift into a new form. 

Other Merfolk that also shift in both ways (that I know of) are the Kelpie ( A Horse Merfolk)  and the Kapa ( A Japanese Merfolk). There are probably more out there but those are the two I can think of right now. 

Question #2: What are Selkie's like?

Selkies are very shy creatures. We tend to yearn for both land and sea and we are friendly by default, which also sometimes makes us very easy to trick, hence all the stories of us losing our pelts. Nevertheless, we are very loyal creatures, and we make very good homemakers. We are very creative and we all have very nice singing voices, though unlike the sirens we can't sing you into an early demise.  

We also have very very very good memories, which is why I can remember about three of my past lives. I think this is how we learn from our mistakes? Personally, no matter what happened in the past, there has always been an endless pool of optimism within me, which I I think comes from the joy of being alive, and being in contact with mother earth. 

I hope that has answered your questions sufficiently :3 

"Happy Birthday!"

"Happy Birthday!"