I haven't tested this specific case myself. The answer might depend on what you might want to do with the mic-only and speaker-only bluetooth device.
How multiple bluetooth devices work with a single android phone:
The android phone provide you with two types to bluetooth profiles to connect to - Phone and Media. Long press on the device listing in the 'Bluetooth Settings', click on options and you can select which profile your bluetooth device should connect to.
The mono hands-free bluetooth headsets can connect to just the phone audio. The mono headset's options in android will not even list the 'Media' profile. The stereo bluetooth headsets can connect to both phone and media profiles. You will find both 'Phone' and 'Media' options for stereo headsets.
An android phone can be actively connected at a time to maximum of 2 devices. One device(Device1) will be connected to the 'Phone' and the other(Device2) will be connected to the 'Media'. All your phone calls will be routed to Device1 and all your music will be routed to Device2. But 2 devices cannot be connected to the same profile at the same time. I have tested this with my 2 stereo bluetooth headsets.
Your request: Connect a mic-only and a speaker-only device to the phone at the same time.
What will not work:
If you want to use it in a phone call so that you can speak through the mic-only device and hear through the speaker-only device, it will not work. Only one device can be connected to the 'Phone' audio at any point of time. For both devices to work together in a phone call they should both be using a phone audio which is not possible.
What might work:
A mic-only device to 'phone' audio and a stereo bluetooth headphone to the 'media' audio might be possible, since both these devices would be connected to 2 different profiles.
I don't know if a mic-only device can be connected to an android device, in the first place. Since devices can either connect to the 'Phone' profile or 'Media' profile and both require speaker output at the other end, I am not sure how it would work. I am specifically curious about how a phone call would work when a mic-only device is connected to the phone profile. May be android would receive audio input from the bluetooth mic and send the audio output to the phone's speaker. Maybe android will show a different profile for the mic-only bluetooth device. The problem is in android I don't see a place where one can choose 'Audio Input' and 'Audio Output' devices like we do in a desktop OS. Mic-only bluetooth devices are used with cameras as shown in this video. I don't know how they would connect and work with android devices.