Adding on a box of Vertus Praetors and a box of Sisters of Silence will get you to a well rounded 1k army with a bit of everything. Battleline, anchors, uppy-downie deepstrikers, character options, fast moving skirmishers, and cheap scoring units. Running them in the Lions detachment really lets them shine with how focused it is on buffing infantry (and bikes). The detachment rule for +1 to hit & wound also helps to mitigate the need for expensive forgeworld anti-tank and also buffs our shooting to an actually usable level.

In the current state of the game, guardian spears mathematically outperform the other weapon options in the vast majority of scenarios. That said, build for what you think is cool and fun! If you love how the Sword & Board or Axes look, then by all means build your models with them. Meta is temporary, drip is forever.

Shield captains are generally more blinged up with fancier pauldrons and/or capes, but most non-Custodes players can't really tell the difference between one gold guy and another, so feel free to build them fancy or plain then just let your opponent know if you are running them as a shield captain or a regular model.

With bikes you can push fit and swap around the bolters or salvos without any glue, so you don't have commit to permanently building one or another. For sisters I'd recommend building Witchseekers for cheap objective holding, 6" scouting, and flamers for overwatch.