The P2SH-P2PK address type is unique to Armory (as far as I know). Unless you want to craft your own transactions, you're limited to dealing with whatever forks Armory has a signer for - you can't just export the private keys and call it a day.
P2PKH is universally supported, and P2SH-P2WPKH is supported by other segwit wallets (assuming they follow the standards).
so ALL Armory legacy addresses are in this unique format? meaning you can't export their private keys to another wallet? makes sense as the root key is unique afaict (2 rows of 9 blocks of 4 letters each, all lower case). that's good to know; don't bother wasting time exporting...
No, you misunderstand me. Not all Armory addresses. For one, P2SH-
P2PK was only introduced in 0.96 and HD/root key wallets predate that AFAIK.
You can choose to have addresses in any (and all) of the 3 listed formats in one Armory wallet right now. I honestly don't remember what the default was when I first booted up Armory, but I suspect it was P2PKH. Up to you to decide which format you use (this is in the settings), and you can check which addresses (used or unused) are in which format via the wallet properties.
Edit: If your addresses are specifically
P2SH-P2PK, then yeah you are going to have a bad time trying to get the exported keys to refer to the right addresses in other wallets. Armory does say that it requires 0.96+ to spend from them.
P2SH-
P2WPKH is a bit less smooth, but doable.
P2PKH is supported by everything bitcoin related that isn't ancient.
Does that help? Don't want to leave you with false ideas about it