Explain me please.

[Urinietszche]

I am new to the game and most of the time of it I spent creating ideologies. So, I stick to the option to get myself custom non-religious usual moral, with default settings to keep the game normal, not making it too easy/nor making it bizzare. There're things I yet quiet don't understand, like ideological building (altar, statues). They come in size variety and have room restrictions (Like if I make exact room it will become shrine or something). I also get a seat (pew) I don't get where to put.
So question is, what is exact role of those buildings and do I benefit from making them bigger size? For example, making huge altar for starting 3 pawns colony seems a bit weird, but maybe I will benefit in long run from it?

[Jaggid Edje]

The altars and ideograms are the same thing, just for different ideologies (you can only have one or the other) are the focal point of the "Temple" room, and are where you will be able to start any rituals your ideology has which use altar/ideogram as the focal point.

The Pews, Kneel clothes, and Kneel pillows are also the same as each other and having the appropriate ones for your specific ideology in the temple near the Altar will improve the "quality" of any rituals that you conduct there which check for them (some do, some don't, it will tell you when you start a ritual if they do).
You place these near the altar, and it will show a connecting line to the altar if it's close enough. They don't really need to be all that close and they do not need to be "facing" a specific direction, at least in the case of pillows and sheets (not sure about pews).

Optionally, you can build a Lecturn in the temple and then the pews/kneel sheets/pillows connect to that rather than the altar. The lecturn connects to the altar in that case. Lecturns also increase the quality of some rituals.

The small/medium/large sculptures are all just decorate. They increase the beauty of the room they are in and having a beautiful temple makes it more impressive, and having a more impressive temple improves ritual quality.
Which you choose to build will depend on what you have the resources for and which ones you set up in your ideology.

At some point your pawns will expect you to build any that you set up and will be unhappy if you do not. The game will tell you when this happens.

As far as the size of the altar goes, same thing applies as for the statues, larger = more beautiful.
It's really up to you which ones you want to set up for in your ideology. The smaller ones will lead to your pawns having the expectation for you to build them sooner, but will be easier to build. The larger ones won't be expected as quickly, will be harder to build, but will contribute more to the room impressiveness and thus ritual quality.
That said, you can get just as impressive of a room with smaller ones by adding some other decorative things, or multiple of the small ones.

As far as your question about making the "exact room", if you build it and make sure to follow the restrictions of no workbenches, beds, etc. the game will call it a "temple".
Gosh I typed a lot more than I had expected to. Hope I didn't miss anything that you asked.

[glass zebra]

To add to that, it's in general:
- Your ritual either requires an altar, then it gets better from having enough rituals seats to seat all participants and from a lectern.
- Or your ritual requires an impressive room (up to 120) and maybe some special item but no altar.
- There are also some rituals which requires neither, but most rituals are either at an altar + its extras or in some impressive room with its focal item.

The statues have similar requirements than the altars (not on bedroom, throneroom or workroom) and can just be thrown into the same room. You can also just chose to not have them in your ideology with no downside. The most "balanced" decision would be to just let the game roll for you and then just change ritual seat / altar to what you find more fitting for your type. Altars are probably more religious in feel than ideograms.