Some advice to start

hello guys, that’s my first post here. i’m italian and my english is not so good, so I apologize if I don’t speak very well, i hope it can be understandable.
i’m planning to set up an HA system with about 20 sensor/actuator with esphome or mosquitto (not sure yet), 4-5 esp32 cam with motioneye, a little weather station, voice control with piper and whisper.
low power consumption is also important for me, so i’m inclined to choose a raspberry board. can RPi4 4gb suitable for my project? is 8gb more advisable? can actually HA works out of the box on 64-bit system?
any advice are welcome.
thanks

Yes

A Pi4 with 4 GB will, based on what you said you want to run, be fine. More RAM won’t hurt and gives you more flexibility in the future.