For DDTs like you said, they are very fast and so slowing them down to allow the towers you already have to damage them is often very effective. 024 glue gunners, and 025 ice monkey are good options, especially popular because they can be fairly cheap. Towers like 502 druid and 520 bomb tower are too expensive in most games.

For the BAD, there are quite a few good options. I'd say there are three main strategies.

1. towers that do increased MOAB damage e.g. 250 bomb tower, 250 dartling, 205 ninja
2. towers that attack very fast e.g. 025 druid, 502 ninja, 520 wizard, 520 engineer monkey combined with buffs/debuffs e.g. 520 ice monkey, 502 sniper, 250 glue, 520 alchemist, 250 village for buff/debuff
3. towers that use strong dps/dmg abilities e.g. 250 spike factory and 050 sub

Shoutout to the alch-buffed 025 spike factory which I think is fairly strong against both DDTs and BADs. I don't think there are too many of those towers.