Mindfulness of feelings and emotions

Vedana is pleasant/unpleasant/neutral feelings at the sense doors. Being aware of that is called Vedananupassana.

Emotions (including for example the five hindrances) are covered under Dhammanupassana.

Here is a simple guide book, How to Meditate, you can follow.

It is customary to memorize these four categories before proceeding with the meditation practice:

1. Body – the movements and postures of the body;
2. Feelings – bodily and mental sensations of pain, happiness, calm, etc.;
3. Mind – thoughts that arise in the mind – of the past or future, good or bad;
4. Dhammas – groups of mental and physical phenomena that are of specific interest to the meditator, including the mental states that cloud one's awareness, the six senses by which one experiences reality, and many others.

Ex: When sitting for meditation, you might feel pain in your legs. That pain is still Vedana(feeling). You can note it as pain... pain... pain... It becomes emotion, if you start to dislike the pain. If you are wishing the pain to go away, you are already emotional. Simply note it as disliking... disliking...

Similarly, you might feel very calm when meditating. Simply note it as calm... calm... calm... If you start to like that calmness, it is emotion. Note it as liking... liking... liking... This liking becomes clinging and when the calmness goes away, sadness/disappointment arises as a result of clinging. That is again Vedana which you can note as sad... sad... sad...

First of all seek the advice of your teacher as mixing other techniques which might not work well with the techniques you are practicing and your teacher will not be able to guide you regarding complication of what you have mixed into your techniques.

There are multiple clarifications of feeling. Three fold classification:

1. Pleasant
2. Unpleasant
3. Neutral

Sometimes pleasant or up plesent is broken down into further 2. i.e.,

1. Pleasant bodily feeling
2. Pleasant mental feeling
3. Unpleasant bodily feeling
4. Unpleasant mental feeling
5. Neutral feeling

See: Vedanā - Attributes on Wikipedia

Emotion pertain you your mental pleasant or unpleasant feeling. Also mental and physical unpleasant feeling influence each other. So if you are mindful of sensations of the body and you do get an emotional disturbance you feel unpleasantness in the body. If you are under physical pain then vise versa is true as well. This is not limited to pain alone but true to pleasant and neutral feelings also. So you if you are mindful of the body you still can feel the mental feelings through the body.

Emotions give rise to thoughts and mental state. If you look at the 121 metal states all states contain Vedana. Also if you look at the metal content which are 52 each of them has Vedana intermingled, i.e., vedana is sabba citta sadharana. (Comprehensive Manual of Abhidhamma) Also the only way to sense any this is through contact with the sense faculties. (Pratītyasamutpāda) Hence only way to know something that happened in the mind or mental content is through the respective vedana arising from the respective contact of the mindd objects and their content. Verada is the unifying factor for all the 4 Satipatthana.

In every chapter the repetition of certain words indicates the importance of this sampajañña. Ātāpī sampajāno satimā applies to the observation of kāya, vedanā, citta and dhammā: sampajañña has to be present. Similarly samudaya-, vaya-, and samudaya-vaya-dhammānupassī, which apply everywhere in the Sutta, have to be with sampajañña and sensations. For example, in Myanmar there are many pagodas on plateaus, with four staircases, one each from the east, west, north and south. Similarly you might start with kāya, vedanā, citta, or dhammā, but as you enter the gallery they all intermingle in vedanā, and reaching the shrine room it is the same nibbāna. Whichever staircase you start climbing, you come to vedanā and sampajañña: and if you are with sampajañña you are progressing step by step towards the final goal.

(Source: Discourses on Satipatthana Sutta - S. N. Goenka)

Also there should be no conceptualisation, imagination, verbalisation, visualisation when doing Vipassana as these are Verbal Fabrication which you are supposed to reduce and calm down. (Cūla Vedalla Sutta, Kāma,bhū Sutta 2, Mahā Vedalla Sutta)

Also Vipassana and Vedana as Understood by a Novice by U Tin Lwin would give a more detailed perspective in some of the concerns you have raised.