As an explosives courier that played so many tours around the Mojave I have to disagree heavelly with people saying explosives are not usefull as your main stat,
they are incredibly usefull as your primary weapons.
You have grenade lauchers, missile launchers, mines, grenades and one of the most übber-gun in the game, the Grenade Machinegun: it's like a minigun, but instead of bullets, it fires grenades.
It's very advisable to have a secondary combat skill and the recommended one is melee, because sometimes enemies close off or you need to enter in close quarters situations, like Vault 34, so you can't toss grenades, dinamyte or use missiles.
The two builds need good DT, so you end up sharing armor and perks between them, they don't need Better Criticals, Finesse or other luck perks (explosives do 0 crit. damage and melee weapons also have very low or sometimes 0 crit. damage) and both skills share more or less the same DAM curve.
Contrary to what Vault.wiki and the Vit-O-Matic machine says, you really don't need high perception with the build, since the attribute only serves for raising skill points and nothing more, so 5 PE (or even 4) is more than enough.
Since you'll raise your explosives skills during the game, it's better to spend points on something else, like endurance, strength or even agility if you are planning to get the Slayer perk (if not, start the game focusing on melee for getting the skill related challenge perk, Melee Hacker, it raises the attack speed with melee weapons by 15%).
If you are taking companions I don't recommend neither Rex, Lily or Veronica, since they attack up close and you need your companions with you, not charging.
Cass and ED-E are good choices, specially because ED-E gain good armor protection if upgraded by the Followers and Cass has the Whiskey Rose perk, wich provides more DT. If you have HH DLC then no doubt you should use Cass, that Large Wasteland Tequila is nasty with her on your party (with 75 Survival this drink gives you +5DT, +2 CH, +30 poison resistence and +5 Strength).
Boone is another good choice, I prefer Cass because +2 CH raises her weapon damage and armor in 10%, but with anyone you will be fine.
And that's it. After having good explosives skills and two Demolition Expert ranks you pick your Grenade Machinegun, some HE 25mm grenades and simply walk inside Quarry Junction, killing those pesky deathclaws as they appear in the horizon, without having to rely on sneak, stealth boy or whatever.
Just put some Wagner on your speakers and do like Col. Bill Kilgore in
Apocalypse Now: I love the smell of napalm in the morning.