Your problem was more likely the fact that your BIOS didn't know you had changed cards. Sometimes you need to do a CMOS reset when changing cards, especially when going from one camp to the other.
Aside from that possibility, no, you should not need to install drivers in order to have a display. Even with no hard drive, and therefore no drivers at all installed, you should still be capable of getting a basic display no matter what kind of output you are using on the card so long as it is
- Supported by the monitor
- Selected as the the input source on the monitor
- No adapters or adapter cables are being used
If there are adapters or adapter cables in use, then other factors might become part of the equation in some cases. None of which is an AMD or Nvidia thing, as I've seen this happen on cards of both types. It is not typical for ANY graphics card so long as it is supported AND it would be wise to make sure that you have the MOST recent motherboard BIOS version installed because that too might be a factor in card support as well.
Beyond that, your image quality is not because of it being an AMD or Nvidia card, specifically. Much MORE likely is the fact that you did not clear out the old drivers and registry settings using the DDU, BEFORE you installed the latest Nvidia drivers. Or, you could have an issue with that card. Or a bad cable. Or your AMD card might be of lower performance and not require as many watts from the power supply as your 1070 does. Hard to say since you don't say what model of AMD card you have OR why you pulled it out.
Knowing your EXACT power supply model would probably be helpful.
Also, this might be something you want to do as well. Actually, all of it, or some part of all of it.
If there are any steps listed here that you have not already done, it would be advisable to do so if for no other reason than to be able to say you've already done it and eliminate that possibility.
First,
make sure your motherboard has the MOST recent BIOS version installed. If it does not, then update. This solves a high number of issues even in cases where the release that is newer than yours makes no mention of improving graphics card or other hardware compatibility. They do not list every change they have made when they post a new BIOS release.
Second,
go to the product page for your motherboard on the manufacturer website. Download and install the latest driver versions for the chipset, storage controllers, audio and network adapters. Do not skip installing a newer driver just because you think it is not relevant to the problem you are having. The drivers for one device can often affect ALL other devices and a questionable driver release can cause instability in the OS itself. They don't release new drivers just for fun. If there is a new driver release for a component, there is a good reason for it. The same goes for BIOS updates.
IF you have other hardware installed or attached to the system that are not a part of the systems covered by the motherboard drivers, then go to the support page for THAT component and check to see if there are newer drivers available for that as well. If there are, install them.
Third,
Make sure your memory is running at the correct advertised speed in the BIOS. This may require that you set the memory to run at the XMP profile settings. Also, make sure you have the memory installed in the correct slots and that they are running in dual channel which you can check by installing CPU-Z and checking the Memory and SPD tabs. For all modern motherboards that are dual channel memory architectures, from the last ten years at least, if you have two sticks installed they should be in the A2 (Called DDR4_1 on some boards) or B2 (Called DDR4_2 on some boards) which are ALWAYS the SECOND and FOURTH slots over from the CPU socket, counting TOWARDS the edge of the motherboard EXCEPT on boards that only have two memory slots total. In that case, if you have two modules it's not rocket science, but if you have only one, then install it in the A1 or DDR4_1 slot.
The last thing we want to look at,
for now anyhow, is the graphics card drivers. Regardless of whether you "already installed the newest drivers" for your graphics card or not, it is OFTEN a good idea to do a CLEAN install of the graphics card drivers. Just installing over the old drivers OR trying to use what Nvidia and AMD consider a clean install is not good enough and does not usually give the same result as using the Display Driver Uninstaller utility. This has a very high success rate and is always worth a shot.
If you have had both Nvidia and AMD cards installed at any point on that operating system then you will want to run the DDU twice. Once for the old card drivers (ie, Nvidia or AMD) and again for the currently installed graphics card drivers (ie, AMD or Nvidia). So if you had an Nvidia card at some point in the past, run it first for Nvidia and then after that is complete, run it again for AMD if you currently have an AMD card installed.
Also, if this is a "no signal detected" or other lack of visual display problem, it is probably a good idea to make sure the problem is not just a bad cable or the wrong cable IF this is a display issue. If it is NOT related to a lack of display signal, then obviously this part is not relevant to your issue.
This happens a lot. Try a different cable or a different TYPE of cable. Sometimes there can be issues with the monitor or card not supporting a specific specification such as HDMI 1.4 vs HDMI 2.0, or even an HDMI output stops working but the Displayport or DVI output still works fine on the graphics card. Always worth checking the cable and trying other cables because cables get run over, bent, bent pins or simply were cheap quality to begin with and something as simple as trying a different cable or different monitor might be all that is required to solve your issue.