Battery advice please

I’d appreciate some advice on the best choice of battery for my classics.

I’ve had issues in the past with corrosion of the metalwork around and supporting lead acid batteries, presumably due to the fumes or vapours given off by the battery. For this reason, I switched two of my cars to AGM batteries to try to reduce this effect.
All cars sit connected to Ctek conditioner chargers (obviously set to AGM for that type).
Would you recommend sticking with lead acid? Is there any great risk of explosion by leaving the batteries continuously on charge? On one car, the battery is pretty close to the exhaust manifolds - any big risk here for an AGM? I was thinking of maybe fitting a ‘classic’ rubber case lead acid battery such as a Shield, as on two cars they are very visible.

This is from in Ohio and does not have water or acid in it, so I think it must be a gel. I think the insides might be made by Optima.

Roger I used traditional lead acid batteries made by Lincoln in all my cars. I don’t have the issue of corrosion that you are experiencing.
Whilst I do have the Ctech battery conditioner I don’t permanently attach it to any of the cars. I only use it periodically during the winter.
I think maybe the constant charging/cycling maybe be causing your battery to give off more gas than normal in storage.
I have kept the use of 2x6 volt batteries in my XKs and single 12 volt in the etype and mk2.

Best regards