The Schiit Bifrost DAC is designed to accept multiple inputs and automatically select the active source. So, it is possible to connect both the Innuos player and the Bluesound 2i streamer to the DAC at the same time. You can then manually select the Innuos player by pressing the corresponding input button on the DAC.
However, if you have concerns about overloading the DAC or amp, you should refer to the user manual or contact the manufacturer for guidance on the maximum input signal levels that the device can handle. Generally, modern DACs are designed to handle a wide range of input signal levels, so it is unlikely that connecting both devices will damage the DAC or the amp.
Regarding your low-end bass issue, it is possible that the built-in DAC of the Innuos player is not providing enough amplification for the low-frequency range. In this case, you could consider using a separate DAC with a stronger output or an integrated amplifier that has a built-in DAC. Alternatively, you could try adjusting the EQ settings on the Innuos player to boost the low-frequency range.