First for Ark Knight, you have the B81 boosters combined with G91, cool enough so you could put HAZEL (tuned for cooling) in place of ANANDA to spare a bit of weight and energy. As a result of the RGB combo, you can tune most of the parts for weight/defence.
The DRYAD missile launcher is rather underpowered for its weight and drain, but it does fire slightly faster and has more range than 69M which is also a single lock missile, but in all aspects it is inferior to the NYMPHE and should be replaced by it (Unless you are roleplaying).
No comment on the arm weapons, as I am sure that you are skilled enough to track targets even with the smaller lock box caused by the lefty sniper rifle, and the PIXIE2 is good enough to kill a lot of stuff on its own.
In terms of optional parts, the EC should be replaced by CR-O69SS to make up for the low stability of the MANTIS that will free up enough space for you to equip O08-RIBOSE for a nice missile tracker. If not facing ECM equipped enemies, you can swap out KANGI for KISSYOH to make it more difficult to be targeted by missiles.

As for FA-001X, it starts out overweight, but you probably have that covered with some weight/leg weight tunes. This is unfortunately a rather squishy middle weight even with tunes.
No glaring problems with the back weapons, though the SATYUROS could probably be swapped out for SPARTOI for a bit more spare weight at a cost of energy regeneration, the latter is made up by the G84P generator. Just remember to only use the SPARTOI at long range and switch to NYMPHE as the target closes.
With the arm weapons, the special lock of the RL with the ND lock of the GOLEM produces a rather small lock box, but it really is up to you though to use whatever fits your style.
For the optional parts, this is one of the cases where the KANGI should be swapped out for MARISHI to free up some of the cooling tunes on the AC.

Can't comment on Delta Fox, as you know, LRp, but it looks like a fully loaded light quadruple designed for close range encounters.