उच्चारणजिज्ञासा - Question about Pronunciation

अँ, इँ एतौ चन्द्रबिन्दुमन्तौ भवतः। अनुस्वारेति स्वरात् पश्चाद् भवेत् । अनुस्वार नैव 'ऊँ' इति रूपवान् नासिकस्वरस्तु भवति पञ्चानुनासिकानां विकल्पः, ते पञ्च व्यञजनानि सन्ति नैव केचन स्वराणां विकल्पोऽनुस्वारेति ।
अँ, इँ are nasal svaras and can't be anusvara. Anusvara as name says follows svara and is an option telling that any of 5 nasal consonants could be here. It isn't vedic chandrabindu which is nasalised svara like ऊँ but just an option for 5 anunasikas that's why no anusvara if there is no need for sandhi.

ततोऽनुस्वारेति प्रयुक्तुमर्हसि तु भिन्न स्वनोऽस्ति।
So you can use just anusvara but it is pronounced differently like a nasal humming after you have pronounced svara. Like you use ओम् first pronounce ओ then without pronouncing m do the humming and then next consonant follows which makes it sound you used the accurate nasal consonant if you speak in quick flow. Chandrabindu is nasalised svara so you ओ and humming are together not separately spoken. Chandrabindu is used only before semivowels in classical sanskrit (e.g. सइँयम written संयम) in spoken only in न् sandhi with ल् in written form (e.g. ताँल्लभते = तान् लभते).

एतन्मे मतो पर्याप्तज्ञानेन मया । this is my opinion with my limited knowledge, though I do recommend trusting gurus