Hello Mary,
First of all you need to post this in the discussion section of the Hoya forum here in Garden Web. You will get more feedback on your questions. This is the exchance section for the Hoya forum, it's for trading cuttings.

Your Hoya Stripes, can you post a picture of it? (on the discussion forum). The box stores (Lowes, Home Depo, Target and Walmart etc) carry an Exotic Angel Hoya named hoya stripes which is actually Hoya Curtisii, if that is indeed what hoya you have. There are about 300 species of hoyas so when you say 'small leaves' it could be alot of them. That's when it's good to post a picture, I personally think it's best to post a picture of the whole plant (to see growth pattern) and then a close up picture of a leaf. Even if you post a picture sometimes you may not still have a definate ID based on the leaves on your hoya, you may have to wait until it blooms.

As for the string of hearts hoya, haven't heard of it. I have herd of string of pearls which is not a hoya. There is a hoya called Kerrii or Sweatheart hoya with actual heart shaped leaves. Here's a picture of a couple of my Kerri's.
Variegated heart leaf kerrii

Hoya Kerrii

Hoya Kerrii 'reverse'

This is not a Kerrii but it does have heart shaped leaves. It's called Hoya Deykeae

Lipstick plant is not a hoya.

I seriously doubt if all hoyas are labeled in the box stores with the name Hoya on it. Some don't even have labels at all. If they do have a label, some of the Exotic Angel hoyas are not names correctly anyway. Confusing I know but just need to get to know your hoyas so if you see one in the box stores you can get it and know it is in fact a hoya regardless of the tag/name.

A website I visit alot in reference to hoyas is http://www.myhoyas.com/index%20ENG.htm

Hope this helps.

shanna

Your string of hearts might be this
Ceropegia woodii String of Hearts
http://www.plantoftheweek.org/week098.shtml
Or there's a Million Hearts Dischidia ruscifolia
http://davesgarden.com/guides/pf/go/59602/
Neither are Hoya's

Tami