Welcome to the rout!
Couple notes on what people have already said. As of Imperium 1
FAQ you CAN take storm shields and ranged weapons. In-fact, I recommend you give every heavy weapon guy a shield. It's a 1 point upgrade from the basic sword and makes the heavy weapon guy quite hard to kill.
https://whc-cdn.games-workshop.com/wp-content/uploads/2017/11/warhammer_40000_index_imperium_1_en.pdf
Cyclone missile launchers are great (for
PL play) and thanks to the designers commentary we don't have to worry about war gear getting dropped. As long as a unit has an option from any source it can be used in any list, even if the data sheet has been updated (!)
https://whc-cdn.games-workshop.com/wp-content/uploads/2017/11/warhammer_40000_designers_commentary_en-1.pdf
Whatever you do, take combi weapons, and lots of them. Save points by taking power/frost swords and bring lots of plasma or melta firepower. Thanks to chapter approved,
WGT's are now a mere 26 points a model, so for a comparable cost to your codex brother's terminator you can have hellblaster level firepower on a deepstriking 2+/3++ frame.
As to flamers I would suggest you only use them for defense. There are a lot of alpha strike armies out there, and one of the best uses for
WG terminators is to give everyone a heavy flame or combi flame and storm shields and deepstrike them onto an objective. 42 points a model with potentially 40 s4/5 hits on over watch (with 19.2 being the average). Get them in cover or out of long range
LOS and they are exceedingly hard to shift. Don't worry about movement though, the enemy WILL come to you.
As with all terminators in this edition, they are weak to 2D shooting and mortal wounds, so positioning is key. (although storm shields help) They can be devastating is used carefully though.
One last thing if you give them the minimum wargear (S.Bolter + sword or shield) It's only 32/33 points a model, making them the cheapest terminators in the game. Not screen levels of cheep but surprisingly cheep for a 2+3++ 2 wound, deep striking model with 2/3 attacks.
Hope this helps.