Thanks for the questions. Please read carefully as these are small but Very important points to differentiate...

Is it OK to record the in-built rhythm patterns to the pattern sequencer?

Or does this not make sense ?

Yes it is Ok and yes it makes sense. It may not initially be clear how this is accomplished or what the differences are. When you activate and Record an Arpeggiator while in the Pattern Sequencer, the data goes from being an Arpeggio Phrase to becoming MIDI Events printed to the Track. They sound exactly the same, but the difference is profound. As events printed to the track, the features and functions that address them are now different. You can now export them in .mid File format. They can transferred to other playback devices. As MIDI events they will playback without you having to interact with the keys.

Arpeggios Phrases are transferred to MIDI Events when you place the Pattern Sequencer in Rec.
To make a *perfect* transfer:
Set “Key On Start” = On — this automates the punch in
Set “Loop” = Off — this automates the punch out

If you attempt to begin recording an Arp Phrase using the count-in and you tried to end recording by stopping the transport before it loops around... unless your reflexes are as good as Lt. Commander Data, or Mr Spock, you missed the mark. You’re probably not that good.

If you are slightly late coming in, your Arp phrase will be printed late (behind the beat), and if you don’t stop the sequencer exactly after the 480th clock tick of the last quarter note, you will get a double hit on the downbeat... since you want to transfer the data, it is highly recommended that you use the provided automation to Punch in/out.

Again, to make a *perfect* transfer of Arp Phrases to the Pattern Sequencer:
Set “Key On Start” = On
Set “Loop” = Off
While making the transfer. This guarantees the start and end point of the Arp Phrase transfer.

Once you have ‘printed’ the Arp data to the Sequencer, it is now treated like any data that you actually played yourself. You will no longer refer to it as Arpeggio. In fact you can turn the Arp Master Switch = Off... and you’ll definitely want to deactivate the KBD CTRL switches on that Part(s)... the MIDI event data will playback without you interacting with the keys. You can simply hit the Play button.

Now that the events are printed to the Track, you can use the Pattern “Play FX” to offset the timing, swing, clock/note shift, etc.etc.
Arp Play FX are used while the data is live from the Arpeggiator.
Pattern Play FX are used on MIDI event data

Did you know?: you can bypass the Arp function [SHIFT] + [ARP ON/OFF] flashes to indicate bypass is in effect.

I have recorded a pattern with one of the preset rhythms however on playback the drums seem weirdly distorted (reverb/eq)?

Did you Record with “Key On Start” = On, and “Loop” = Off? Probably, not. For a *perfect* transfer... use it...
Also once the Arp data is transferred to the Pattern Sequencer remember to either disable the Arp, bypass the Arp, or turn KBD CTRL to inactive for those Parts. If you do not — touch the keys will start the Arpeggiator (in addition to what you’ve recorded).

In any case if you want to record say, a bassline over a preset rhythm pattern, the rhythm pattern will also be recorded won't it?

Or is it a matter of turning off keyboard control?

When you wish to add a Part to your Performance, it can join in one of two states:
1) You play it simultaneously with your other instruments... or 2) you play it by itself.

To Layer or not to Layer
If your goal is to add a Part to your Performance to create a Layer or a Split, then, naturally, you want to have KBD CTRL active for both instruments. Correct?
If your goal is to overdub a bass line to an existing drum Track, then, naturally, you DO NOT want to have KBD CTRL active for both instruments. Make Sense?

Each Part has its own dedicated Track.
If you are playing a Part (if you touch the keys and can hear it) then it’s dedicated a Track is going to record it. If you have two Parts linked by KBD CTRL and either one of them is selected - they both get recorded to their own Track. It is that simple.

But don’t think just because KBD CTRL is green that this is the Part you are playing — that would be not necessarily true.

Here’s how this works: the Part you *select* (highlight) is the Part you are playing.
Even if four Parts have KBD CTRL active, Parts 1-4, you could still *select* Part 5 and play just Part 5... and it has no KBD CTRL active!!!
However, selecting any one of the first four Parts is like selecting all four of them... because they are linked (all for one, one for all four) ...bad pun

You can play the KBD CTRL linked Parts by selecting any one of them (they all work together). But if you directly select any of the non-linked Parts you are playing just that one Part.

So turning Off KBD CTRL is a partial answer... and in fact is not even necessary... what you hear when you touch the keys is what gets recorded. So it is the *select* that determines what gets recorded — follow the highlight.

‘Don’t let this hurt your head‘ (a favorIte saying of one of my teachers when revealing a mind-blowing fact): when you tap KBD CTRL to deactivate it, you‘ve actually *selectEd* that Part!

Point bring... KBD CTRL can affect what gets recorded, but really it is what you have currently *selected*.

EXTRA CREDIT:
Use KBD CTRL LOCK = ON when sequencing — what it does is make it so only the Part you select sounds, it does this by locking KBD CTRL to Part 1... now when you add “+” a new Part, it does not automatically LAYER with your previously added Parts.
Tap “FX” top center of the screen
Turn “KBD CTRL LOCK” = ON
now... only one Part can play at a time.

To defeat this, simply touch KBD CTRL to activate it on the Part you want to Layer.

Hope that helps. Thanks for the question.