Currently there are 2 types of storage water heater tank technology,

a. Enamel-coated technology - newer technology, better leak resistance, and cheaper. CENTON (example here - Shopee / Lazada) and ALPHA (example here - Shopee / Lazada) is using this technology.

b. Stainless-steel technology - old technology, more prone to leaking, and more expensive. JOVEN (example here - Shopee / Lazada) is using this technology.
I suggest u to go for CENTON. By far the best-selling and highest 5-star rated storage water heaters on Shopee, and cheapest amongst these 3 brands too.

Currently there are 2 types of storage water heater tank technology,

a. Enamel-coated technology - newer technology, better leak resistance, and cheaper. CENTON (example here - Shopee / Lazada) and ALPHA (example here - Shopee / Lazada) is using this technology.

b. Stainless-steel technology - old technology, more prone to leaking, and more expensive. JOVEN (example here - Shopee / Lazada) is using this technology.
I suggest u to go for CENTON. By far the best-selling and highest 5-star rated storage water heaters on Shopee, and cheapest amongst these 3 brands too.

If I'm not mistaken, most enamel-coated storage water heaters uses mild steel underneath the enamel-coating.
I believe u can conceal it anywhere as long as that area provides sufficient space, water pressure, and electrical component & wiring that caters to the storage water heater's minimum spec requirement.

But make sure to provide sufficient access opening (eg. manhole) for future maintenance, enough room for the storage water heater's dismantling process or servicing work, or else u will be charged for breaking and reinstalling of your concealed area (eg. plaster ceiling).