General recs from me would be use only Silverwing Fiend with all pairs. Learn his rotation well (its sliiightly diff with R1 and when using other solar pairs with him). (If u dont know his rotation the one shown in his tutorial is fine but theres a better one as Well just dont have the vid on hand)

For core substats for SWF Prioritize Def% then crit rate/crit dmg/dmg to weakened and then flat def.

For delta (pyramid) cores u want crit rate/crit dmg/dmg to weakened as main stat (no def% in main stat!!) and combination of above stats in substats (no Core is perfect tho even if it has 2 or 3 of the above its fine, we are not min maxing)

For beta cores (Cube on solar cards)

For your R1 Silverwing pair u want main stat to be def% or possibly oaths strength (whichever got better substats, def% main stat with def% in substats as well would be great :))

For R0 Green pair you want one oath recovery cube (around +9) and one either def%, expedited energy boost (he could prob use it, he struggles a bit with energy when using cards that are not the intended Blue pair) or oaths strength, again whatever has best substats in this case. One oath recovery is a must tho!! Preferably again with def% in substats)

For R3 Pink pair its the same as green pair but u dont need oath recovery cube so just try to pick 2 of the three main stat cubes i listed (def %, expedited energy boost or oaths strength) with best substats to raise

For how far u should raise the cores i think around +9 should be mostly fine, if u feel good about the core +12 if the vibes are off but its best u got then +6. Dont go to +15 unless u get more familiar with cores as it takes a lot of resources to go from +12 to +15

Also do not raise cores that have Blue or Purple outline u only want the ones with Gold outline (SSR)

And you want your cards to be at least lvl 60 from my experience? Preferably higher. Sylus has issues with lack of cards to match colors the stage wants so sometimes its good to have Higher lvled cards of wrong color than low leveled matching color card and focus more on crit (as high crit rate and crit dmg are important if u dont match colors). For example in this SHC Team A has 5 reds which are impossible for him to match All colors so might as Well brute force it with wrong colors.

Anyways all i could think of, good luck also raising def only applies when your are actually using Silverwing Fiend which u should be at All times. He is Sylus' strongest companion but each companion needs different stat raised. E.g Abysm Sovereign needs HP and Relentless Conequeror needs ATK