So, i'm working on crafting the famous Rad II Kopesh (well, in my case it's a rapier since i'm a dex build) for my Assassin III Dual Wielding Finesse Rogue.
It's my first time messing around with greensteel and i'd strongly appreciate some advice:

The weapon i had in the crating planner would be

A +5 GS rapier
Tier 1: Holy
Tier 2: Flaming burst
Tier 3: Fire blast ('Flame burst' +4d6 fire on vorpal)
Bonus 1: Aspect of Radiance I (sunbrust 2xday)
Bonus 2: Aspect of Radiance II (blindness + 4d6 light damage on crit)

Ok, now i don't know how this works so hopefully you guys can help me improve this by answering some questions:
1- Would Flaming Burst and Fire blast Stack ? (crafting planner pre-made recipes seem to sugguest so, but doesnt hurt to be sure) Also, i'm concerned about the viability/usefulness of having fire on my weapon end game wise (thought it would help me when TRed in the 12-16s, but even so i wonder if there are better options). The packs i mainly run are Vale/Secrets of Artificers/Canith Challenges/ Orchard to some extent and might buy Reaver's Reach soon. Then again, it seems like it's the only damage element after chosing RadII so guess i don't have much choice

2- Do i have to craft a Bonus 1 to be able to craft the bonus 2 radII? Because quite frankly sunburst seems quite useless.

3- Also, for my other hand i was planning a purely dps rapier (perhaps LitII?), any suggestions on that? (since there i no paralyzing, thou i can tell i'll probably be switching to RadII+ Epic Envenomed Blade quite often) Other great option would be instead of going for pure dps on the offhand going for Acid+Acid Burst + Acid blast + Stone Grab (35 reflex) which one do you guys reckon to be best?

Ok that's about some of the doubts i have, thanks for reading this and please share any bits of experience you might have to help a beginner :P