Only Naval officers.
It is very effective specially in early days due to its max range and can protect against airforce and sub too.

They’re worth it, tho in general more of a force multiplier.
Build at level 1 and then just keep upgrading.

Yes, absolutely. You just have to be very careful not to lose an officer, especially once you have upgraded it.

My friend stacked infantry officer with towed artillery, a beast i tell you.

Naval Officer is a must have :

1. Costs 0 Electronics
2. Only takes Nav2
3. Basically 3 ships ( frig; cruiser and destroyer) in 1.

Others seem like a waste IMHO; but only other one ever used was fixed air wing but his stats really not that much better. But a Nav Officer is a game changer.

Personal Officer Tier-list. I play air + frig support, for reference.

God-tier (S):
- Naval Officer: As @The Pale Rider said above, no elec cost, easily accessible, extremely versatile. Build him ASAP then keep upgrading him alongside your fleet and you will have a hell of a naval fleet for both offense and defense. And unless you send him to a solo suicide mission, most likely he'll last you till the end of the game. The only games where I don't have him built is when I play land-locked countries.

Great (A):
- Submarine Commander: His speed buff offset one of sub's weaknesses: slow speed. Mix him with a standard navy stack can allow for hit-and-run tactic which is tremendously powerful in competitive play.

Good (B):
- Fixed Wing Officer: Extremely fast solo flight speed, give damage and speed buff to the stack and he's counted as a different unit type so besides his army boost, he is great for damage mitigation, especially for flimsy fighter stacks. His downside is there's only one of him and most air-focused players would have several stacks of fighters everywhere. His cost is also significant compared to what he could bring to the table so most of the time I'd rather build additional aircraft at early game than saving up for him and by the time I have him built usually my aircrafts are already at T2. He's a nice-to-have factor if you are already snowballing and want to absolutely curb-stomp a game.

Meh (C):
- Tank Commander: Despite his name, don't use him with an armored stack. In fact, don't use any Armored stack, period. Wait, then how do you unlock him? You could unlock him after unlocking T1 Tank Destroyer for holding down cities. Mix him with a stack of MLRs and/or SAM for a huge damage boost and a significant speed boost to outrun your enemies. Since Artillery and Naval Units have this attack-cooldown-gets-reset-to-1-minutes-after-destroying-a-unit feature, stacking him with 9 MLRs and have that stack accompanied with a stack of SAM+radar for an nice and easy cruise through the enemy territories. Until they launch like 10 cruise missiles at your MLR stack while your SAM's AA is still on cooldown, that is.
- Rotary Wing Officer: think fixed wing, but retarded. Some people swear by Heli as a feasible, niche unit type, on the other hand, I don't see them winning in any of my game. If you're going Heli route already, he's like B-ranked. His saving grace is that he doesn't cost Component to build and at T3 he's can fight Sub, but by the time you unlock T3 with your rank you must've wisened up against playing Heli already.
- Airborn Officer: RIP to people not reading his skill before building him and thought he's like a better Airborne Infantry and could grab land on his own. He can't, because at level 3 research he turned into his true self, an expensive Special Force unit who can't scout, have no radiation protection, you know, all those skill which a lvl 1 Special Force unit has. Oh he's special alright, but not the good kind.

Literal trash (F):
- Infantry Officer: He's S-tier when he's built by your opponent. I frequently check for anyone building Infantry Officers in CoN News. Those players then becomes my top targets for invasion. Literal newbie trap. Expensive to build, useless in most cases. His pseudo-radar can't detect infantry, or literally anything other than Hard target. On top of which, while Naval Officer can already do the job of all 3 type of navy troops at level 1, this bitch ass deadbeat of an officer can barely do the job of a Naval Infantry at Day 18 when his penultimate research is completed.

Inb4 someone fix their glasses and say "acksually": I know Officers are supposed to stay with a stack because their value mostly lies in their Army Boost. But for some unit type where going solo is their main selling point (infantry) and getting into a stack is just a secondary function, the officer having less feature to offer than their supposed subordinate is a joke.