I belive you mean hmc980lp4 instead of hmc980.
pin 19 is trigout, i think thats a typo and we are talking about pin 17 & 18.
The shunt bypasss caps you place between vdrain out of ABC and suipply pin of the AMP is mainly related to the PSU you are using. If you are using a regulated supply than you can be OK with less number of CAPs. Please refer to FAQ on the link below.
https://ez.analog.com/docs/DOC-11963
The attached circuit is tested and verified for biasing HMC637lp5e w/ hmc980lp4e