No, I don't think it matters if you use DevaCurl or Care -- maybe the DevaCare might be better on your scalp? Maybe there's something in the DevaCurl you are a allergic to? I've never gotten a real itchy scalp, maybe once in awhile I notice it when I switch brands but I think it's just my scalp adjusting to new things? I've used the DevaCare line also and it's great, I love the ArcAngell (YUM).

As far as my routine:
Once a week, wash scalp and rub through - No Poo, massage very well and rinse
Everyday - use three (or maybe a little more) pumps of DevaCurl One C - put throughout hair and let sit while I finish showering; Rinse, just a little, not all the way and then flip hair upside down, do a bit of scrunching, while I have my hair in the "scruched" position in the front, tilt my hair back up, shake head a little to position curls
Use Curlease to scrunch the drippiness out, gently
Apply DevaCurl Angell right side up, scrunching gently and then tilt upside down to get underneath and scrunch a bit of gel in
Once right side up again, I clip the front of my hair to get it to lay where I like it, and then air dry (until my DevaFuser gets here!)
Once a week, instead of using One C, I use Heaven in Hair the same way I do One C except I rinse a bit more.

I hope that helps! Oh, and if I don't have or use DevaCurl that day, I use biolage, which also rocks! But, lately, I've only used DevaCurl, but biolage would be my second choice.
Cowash - No Poo
Conditioner - One Condition
Gel - Light Defining Gel

Looking to try Devacurl Decadence line next! Can't wait to try it.