Well, nothing wrong with Samsung 25R in a mech if your build is right, yet many long time mech users that lean toward the safety side like to have that extra spike/short headroom a Sony VTC3/4, or LG HB6 offers in case of that fire in the pocket or an insulator melts down, and with the rap sheet the Cherry Bomber has, better to be safe than sorry with that, even though the
batteries are in parallel I believe.
OP
28 or 26 awg wire will be fine, 28 preferably if you are just getting into rebuilding. Get yourself a decent ohm reader, brush up on your battery chemistries, battery safety, Ohm's Law and such, then start doing virtual coil builds at this website here ->
Steam Engine | free vaping calculators a lot of nice
vaping tools there for you, and start playing around in there with different diameters, number of wraps, check amp pull by using the ohm ratings you are doing in steam engine's coil builder tab. As stated above, 0.4 to 0.5ish in ohms rating should be the lowest target you should be going for if starting to build, 0.4 should be around 2x 2.5mm id coils 6full wraps/5half wraps, will hit between 0.4 and 0.5 and still perform nicely, pulling 10.5amps at 44.1watts.