Individually, they are both very beautiful combinations. (Especially Harvey Angelo as both pieces are names that I favor).
On a personal level, I would only use one (Angelo/Angela) just because it's a little much. However, I don't think that there's anything too terrible about using them for twins. They would tucked away in the middle and therefore, not something the kids would have to deal with on a daily basis. The pair, Harvey and Olivia, sound equally classic and polished as well as sleek and modern. I like the idea of a secret connection for twins in the middle slot though.
You might consider Harvey Angelo and Olivia Evangeline OR Harvey Antonio and Olivia Angela, for example.
I like Harvey and Olivia as a pair. There's a subtle connection (6 letters, includes the letter V) but without being too 'twinny', if that makes sense. I think the middle names are far too close, though. I'd change Olivia's to something else, it feels a bit off with both names ending in the -a sound.
Harvey Angelo is an absolute winner. Very unique, in a good way.
Olivia is orders of magnitude more popular than Harvey (except in pockets of the UK), but it remains a very pretty name.
Angela is dated and not as classy (imo) as your other three choices. "Olivia Angela" doesn't flow well-- they both end with the same sound, and saying it quickly is hard due to the ending vowel of Olivia and starting vowel of Angela.
I agree with other posters-- switch up the angel name for the little girl. That way you'll maintain a connection, but it will be a bit more subtle, and you'll have the added bonus of a more melodious flow. There's not too many choices I can think of...
Malak [Arabic for 'angel,' a common name]