Multiple scenarios per feature is fine, so long as they are logically in the same area. If you are attempting to address a different use case I would probably suggest making it a new feature. In your case, it looks like the two scenarios would fit fine under the same feature.
Scenario Outline is analogous to TestCase
in NUnit, you would only use this if the same scenario structure just needs to take different parameters.
The SpecFlow github site has good documentation on Scenario Outlines here. I will summarise the code sample below.
Given two scenarios in a feature:
Scenario: eat 5 out of 12
Given there are 12 cucumbers
When I eat 5 cucumbers
Then I should have 7 cucumbers
Scenario: eat 5 out of 20
Given there are 20 cucumbers
When I eat 5 cucumbers
Then I should have 15 cucumbers
You can parameterise repeating parts using an outline:
Scenario Outline: eating
Given there are <start> cucumbers
When I eat <eat> cucumbers
Then I should have <left> cucumbers
Examples:
| start | eat | left |
| 12 | 5 | 7 |
| 20 | 5 | 15 |
This outline replaces the scenario definitions you are trying to parameterise.