Also, if i'm not mistaking, softserial interferes with timers, interrupts, millis().
SoftwareSerial does interfere with interrupts (and therefore also millis()) and Altsoftserial does interfere with timers (it uses Timer1 exclusively). And Altsoftserial is fixed to pins 8 and 9 and you cannot use pin 10 as PWM. Both implementations are by far not as robust and reliable as the hardware serial.
The network can work on a higher baudrate if altsoftserial is used. softserial makes the hardware serial have limits.
That's correct, because it's disabling interrupts while sending and receiving.
But you haven't provided a reason yet why you have to use both, SoftwareSerial and Altsoftserial. And as far as I can see, you could even use hardware serial on the "UNO"-Chip.