An Arduino is NOT a simulator. It is a real physical microprocessor in a convenient package for experimenting coupled with a the Arduino IDE software which makes programming easy for beginners.
The connectors on an Arduino Uno or Mega would not be sufficiently robust to incorporate those devices in a product that was expected to operate reliably for a long time.
But you can get Arduino boards that can take soldered connections.
You can also develop a project on an Arduino board and then build a product on a custom PCB using the same Atmega MCU and the same program. This could include (for example) developing a program on an Uno and building a PCB with the surface-mount version of the Atmega 328.
The Arduino IDE can also be used for programming other Atmega chips (such as the Attinys) which are not built into any Arduino board.
The other great advantage of the Arduino system is the wide range of devices that can be used with it and the many specialized libraries to make using those devices easier.
It sounds like you would benefit from getting an Arduino Uno and experimenting with it. The Arduino system is very good for learning-by-doing.