Naganadel+ttar was the initial core as they complement each other pretty well. Naganadel ohkoes pokemon like urshifu, genesect, kartana, zygarde,tapu fini, tapu lele while deals great damage to rillaboom, tsareena. In turn ttar koes av kyub, deals psyspam for naganadel. Initially zygarde was added as the next mon but then i realised dd kyub would be a better fit that zyg. Dd kyub shares and excellent offensive synergy with naganadel. Naganadel deals kart, gene, urshifu, scarfed lele and pult for kyub while kyub deals ground types for naanadel and ofc eases the bad zygarde mu of the naganadel+ttar core if naga gets locked into other move. kyub also checks amoonguss which i thought was quite a trouble for naganadel. Urshifu was the next as ttar deals incin but some some mons with intim like scarfty even if its rare totally shuts the core and even diancie/p2 were quite a problem. lorb shifu was chosen for protect as most mons in the teams lack it. rillaboom was the next mon added due to fake out and as a terrain shifter as misty terrain dampens draco meteors power. rillaboom also provided with u turn which is much appreciated by kyub and added a nice priority. Superpower rilla improved the kartana mu further. Mew was added next too purely support kyub's setup and counter full tr teams. Till this moment the ttar was av but now I changed it to shuca+rocks to have a good move on mew which supported set up. I didn't think a second fake out was required so went for coaching instead as coaching also helped urshifu acquire hella power and ohko almost everything after +1. Transform is just so great in conjunction with dd kyub as it facilitates easy pressure on the opponent by transforming to kyub or smth the opponent started setting up and was causing a problem.
For example -
https://replay.pokemonshowdown.com/gen8doublesou-1385502555-1s5djrhho0snv66m542d65cwtl509mypw
In the end scarf naganadel is a cool mon that has its own niche which nothing would do better than it itself does. The team struggles a bit with metagross but things like flamethrower+cc/fusion bolt/lash out help even break through it. Modest on naga was necessary to pick koes on urshifu and scarf lele+modest also boosts spa which can come in handy for some situations.