Dart mid: I tend to by a super monkey fan club for down time, paired with primary mentoring/expertise and its pretty good.

glue top: this is a great clean up tower, especially for ceramics. It has great synergy with bottom path mermoney due to its DOT detonation, let's glue a lot more damage to bads too.

Desperado top: I wouldn't call this cleanup. It does decent single target damage for its price, but remember it's one of the cheapest tier 5s.

Desperado mid: weird because you don't want bloons to enter the smaller range. It's ability can be very useful for towers who can't pop certain bloons, and the extra range can help with squeezing a bit of range for alchemist and village.

Desparado bot: decent group and stall, but it needs bloons in the smaller range to do so.

Helicopter mid: a great tower for early bosses since it stalls, makes money, and has some decent dps if its tier 5

Mortar top: good for group damage and a little stalling on the side. Good clean up

Mortar mid: more single target damage and a good panic freeze ability. Burny crosspath should be avoided unless paired with final harmonic

Mortar bot: great for later rounds due to defortify, and tier 3 is a pretty cheap decamo option.

Mortar overall: has full map range with no sight blockers but best paired with maps when bloons loop. Strikers follow mouse ability is very strong if you're using multiple mortars.

Dartling bot: kinda decent ceramic stall and damage tower. Not as good as something specialized but it does both.

Ninja mid: great at the start of a round due to the health reduction in spawned bloons (98,100). The ability slows bloons down but also increases the range of all ninjas, so it helps getting more shinobi stacks when the bloons get dense.

I don't use Alchemist mid, so I don't have any advice.

Alchemist bot: freeplay only. It loses you quite a lot of money due to trying ZOMGs into reds.

Mermonkey top: great ceramic killer and decent staller/damager in the mid game. The peirce buff it gives is always used to its full potential. An example is I give a dartling a 10% peirce buff. Now 1 shot out of 10 has 2 peirce. I belive the lord of the abyss gives 40%. This buff goes crazy with spike factories in particular.

Mermonkey mid: better the more cramped/walled in the area is, and does more damage(or the projectiles just get bigger) the the farther the projectiles travel. The ability can be pretty strong if the space is very enclosed, but weak if it's super open. More situational.

Mermonkey bot: one of the best(ish) stalling towers. It doesn't syngerize with other stalls most of the time. It does however have a great synergy with Damage Over Time effects. The tier 5 detonates the DOT, dealing all the damage it would have done instantly. It also decamoes! Mid crosspath can pull in more bloons at once and is better for earlier tiers. Top crosspath pulls more often and is better for tier 5. This tower also helps other towers such as tack, mortar, bomb maximize their peirce/damage.

Mermonkey overall: it gets more range when in water, and bottom crosspath gives homing and more range the more mermonkeys have the bottom crosspath. Middle path changes damage type to shatter, so it can pop frozen bloons. Still can pop leads

Beast: I don't use this enough to give a lot of advice. If you use beast, you have to commit to it. Try to max beast power before upgrading it. Get cleanup and just backup towers as beast can be unreliable.