1) Does the tape thing hold the hair as well/securely as glue?
I only tried one type of tape and the answer for me was no. I always added glue. I noticed with the glue though (I wore the full lace wig in the summer) is that the glue always seemed to look shiny like it was not dry. I rocked it anyway. The first time I had it professionally installed then I started doing it myself becuz I washed every week. Very time consuming by the way to clean my wig, let it air dry and complete my regimen.
2) What happens to the back of the wig? In the application videos it looks like they only secure the front but do nothing with the back. Can you wear your hair in a pony tail and sit still look natural? If its a full lace wig you can glue it down as well (I did) but was never brave enough to wear an updo. Or you can use wig clips. If it is a front lace only it will probably have a band or comb in the back to secure it. Many people do wear ponytails and updo hairstyles I always felt self conscious though with the full lace bcuz it wz kinda messy back there or a small section would not stay down.
3) How do you sleep with it?
Just wrapped the hair in a satin scarf or braided it in two braids and wore a bonnet.
Yes, if the wig cap is too tight it will cause trouble. I had matching bald spots about the size of a dime on each side of my temple. I wz in so much pain one morning in church that I had to borrow scissors from the office to cut the wig cap of both sides to relieve the pressure. I graduated to fleshtone pantyhose which were looser and still gave me a natural look whenever I parted my wig. The satin scarf is safe but may show if you wear parts.
Also - I started buying synthetic LFwigs and never use glue just bobby pins, and the combs or bands that are attached to the wig. No glue or residue to clean up or worry about and I can remove it every night to moisturize my hair. I normally wear them in the winter if at all and I wear a plastic cap covered by a stocking or wig cap then the wig. So I am baggying all day and my hair is moist, warm and safe!
p.s. I am by no means an expert - this has been my experience.